Des utilisateurs ?
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Anonyme
1478
Sujet de la discussion Posté le 24/01/2009 à 21:25:35Des utilisateurs ?
Bonjour
ce truc m intereese...ya des utilisateurs ?
ce truc m intereese...ya des utilisateurs ?
aKhemist
53
Posteur·euse AFfranchi·e
Membre depuis 8 ans
2 Posté le 21/09/2016 à 02:58:34
Up la meme j'ai une vielle nes a faire bosser
TekE7
495
Posteur·euse AFfamé·e
Membre depuis 20 ans
3 Posté le 21/12/2022 à 11:12:01
Deuxième déterrage
https://wayfar.net/0xf00000_changelog.php
https://wayfar.net/0xf00000_changelog.php
TEK E7 electronique analogique, studio & sound system
TekE7
495
Posteur·euse AFfamé·e
Membre depuis 20 ans
4 Posté le 21/12/2022 à 11:22:50
Le manuel
USING MIDINES 1.1.0______________________________________________________________/\
_______________________________________________________________________________________________
_______________________________________________________________________________________________
____ USING CONTROLLER #1 ______________________________________________________________________ /\
_______________________________________________________________________________________________
____ MIDINES MODES____________________________________________________________________________/\
PRESSING SELECT ON THE #1 CONTROLLER TOGGLES BETWEEN MODES 1 and 2.
MODE 2 is the default, Mode 2 allows the screen graphics to run so that you can monitor the note sprites and also use NESFX.
MODE 1 disables the Graphics routines, which silences that nasty 60 hertz buzz, and also increases Music processing performance.
You will notice a significant sound difference between MODE 1 and MODE 2 when using things like the pulse mod hack, and the DMC Wave Traveller. So usually it's best when composing to choose the MIDI Channel offset you need and then turn Midines to Mode 1 and just keep it there for the entire composition.
_______________________________________________________________________________________________
____ MIDI CHANNEL OFFSET_______________________________________________________________________/\
PRESSING UP ON THE #1 CONTROLLER INCREMENTS THE MIDI CHANNEL OFFSET.
PRESSING DOWN ON THE #1 CONTROLLER DECREMENTS THE MIDI CHANNEL OFFSET.
NESFX must be OFF, and Midines must be in MODE 2 in order to change the MIDI Channel Offset.
-The default Midi channel assignments for Midines:
MIDI Channel 01 = Pulse 01
MIDI Channel 02 = Pulse 02
MIDI Channel 03 = Triangle
MIDI Channel 04 = Noise
MIDI Channel 05 = sample (DMC) channel
Can be changed, rather shifted - to respond to different MIDI Channels using the UP / DOWN pad on Controller #1 .
The on screen channel displays the current base channel.
This defaults to MIDI Channel 01, which will be the current MIDI Channel the Pulse 01 audio channel responds to.
If for example while Midines was in mode 2, (toggle with START button) and you pressed up twice the channel display would now read channel 03. This sets the Pulse 01 to respond to MIDI channel 03. Similarly the other audio channels will have been shifted up by 2.
-channel 03 - MIDI Channel Offset
MIDI Channel 03 = Pulse 01
MIDI Channel 04 = Pulse 02
MIDI Channel 05 = Triangle
MIDI Channel 06 = Noise
MIDI Channel 07 = DMC (sample) channel
Offset "a" is hex for decimal 10, "b" is 11.
_______________________________________________________________________________________________
____ NESFX___________________________________________________________________________________/\
Pressing START on the #1 CONTROLLER toggles NESFX ON/OFF.
Basically NESFX changes the graphics on screen based on things like channel pitch, or notes played.
_______________________________________________________________________________________________
______________ AUDIO CHANNELS + EFFECTS_______________________________________________________/\
_______________________________________________________________________________________________
The NES features 5 sound channels, 2 Pulse with 4 step variable duty cycle, and 4 bit volume control. One triangle wave channel, that unfortunately has no volume control. One noise channel with two different random waveform generation methods, a short and long loop period (same as GB). Lastly a Delta Modulation audio sample channel.
Even though Midines has a few built in ways to modulate things, the MIDI latency is low enough in mode 1 that you can modulate any parameter into the audio domain, just using your sequencer application and MIDI CC commands.
Details on each of these sound channels follow.
_______________________________________________________________________________________________
______________ PULSE CHANNELS_(MIDI 1,2)________________________________________________________/\
_______________________________________________________________________________________________
The pulse channels feature 4bit volume, 4 duty cycle settings, a sweep pitch feature, and an auto volume envelope feature. The pulse channels can also be modulated via a modulation hack that constantly resets the pulse waveform generator.
Note on velocity allows 16 volume steps, and is derived by dividing the mid note volume by 8. Therefore changes in velocity of less than 8 may not have an actual effect on the sound channels volume level. Also some sequencers do not automatically set the master volume CC7 to 127. This master volume setting must be at 127 on order to get the full volume range of velocity from the midi notes you are playing. The master volume takes precedance over velocity and scales the velocity accordingly, however remember there are only 16 steps to the volume. Therefore if the master volume CC7 is at 7 or less the channel will *not* sound at all, even when playing a note at 127 velocity.
You can use midi pitchbend to shift the pulse channel it's entire frequency, if the stepping you hear is rough it could be due to your midi controller not sending incremental midi pitchbend messages, ex. 1001,1002,1003,1004....1212,1213 these would provide a smooth pitch bend, however many keyboard controllers default to larger pitchbend increments, ex. 40, 64, 80, 128 this will cause the pitch transition to sound rough. So check your manual for a pitchbend resolution, or look to use the "fine" pitchbend for vibratos over rough. However there is way around this by using MIDI CC8, which is a fine pitch bend that runs off MIDI CC8.
Fine Pitch CC8 offsets the fine pitch register for the note only. So due to this some notes may wrap from low to high or high to low pitches.
The NES has another important hardware setting related to the avaliable frequency range of the pulse channels.
In order to play the lowest octave notes on the pulse channels you must make sure CC 16 = Sweep Shift, is at full on (127). Midines defaults to this setting, however if you start working around with the sweep and suddenly loose the lowest octave of a pulse channel, thats the reason.
PULSE MIDI CONTROLLER CHANGE MESSAGES (CC parameters)
OFF = less than 64 (0x40)
ON = greater than or equal to 64 (0x40)
Mod wheel / CC1 = Duty Cycle
CC7 = Master Volume (value overrides note velocity)
CC8 = Fine pitch mod
CC9 = Pulse channel length envelope
CC10 = Toggle OFF/ON pulse channel loop envelope
CC11 = Toggle OFF/ON volume Envelope disable
CC12 = Toggle OFF/ON Modulate pulse channel
CC13 = Toggle OFF/ON Enable Sweep
CC14 = Sweep Down / Up
CC15 = Sweep Period
CC16 = Sweep Shift
_______________________________________________________________________________________________
____ MOD HACK________________________________________________________________________________/\
MIDI CC 12 (Toggle OFF/ON) turns on the mod hack if you send a value of 64 or greater, (0x40).
MIDI CC 6 is the frequency for this routine. _______________________________________________________________________________________________
______________ TRI CHANNEL_(MIDI 3)_____________________________________________________________/\
_______________________________________________________________________________________________
The triangle channel does not support hardware volume control as do the pulse and noise channels. Despite this limitation the triangle channel features the widest frequency response that the NES has to offer.
MIDI pitchbend allows full frequency shifts.
TRIANGLE MIDI CONTROLLER CHANGE MESSAGES (CC parameters)
CC8 = Fine pitch mod
_______________________________________________________________________________________________
______________ NOISE CHANNEL_(MIDI 4)___________________________________________________________/\
_______________________________________________________________________________________________
The noise sound channel features 4bit volume control, and also has an auto volume envelope feature, similar to the pulse channels. The noise channel has 2 modes of noise generation, long loop and short loop.
Long mode allows for standard noise generation, and short mode sounds more metallic and less random, more periodic. The NES's long / short noise loop modes are similar to the Game Boy noise modes.
The noise channel is spread out over MIDI channel 4. Due to the limited 16 noise pitch/period values that the NES allows, the noise period is repeated every 16 notes. For MIDI notes above 64 inclusive (64 dec 40 hex), noise short loop mode is set to on. For MIDI notes below 64 (64 dec 40 hex) the long mode is on.
Note on velocity allows 16 volume steps, and is derived by dividing the midi note volume by 8, scaled by the master volume. Therefore changes in velocity of less than 8 may not have an actual effect on the sound channels volume level.
NOISE MIDI CONTROLLER CHANGE MESSAGES (CC parameters)
OFF = less than 64 (0x40)
ON = greater than or equal to 64 (0x40)
CC7 = Master Volume
CC9 = Noise channel length envelope
CC10 = Toggle OFF/ON noise channel loop envelope
CC11 = Toggle OFF/ON volume Envelope disable
_______________________________________________________________________________________________
______________ SAMPLE CHANNEL (DMC)_(MIDI 5)____________________________________________________/\
_______________________________________________________________________________________________
The sample channel in Midines 1.1.0 features 256 different samples grouped into two 128 note sound banks. Samplesets include, TR909, TR808, TR707, LINN, AMEN, VG, HONG KONG BATTLE ACTION!, as well as additional breaks, and the older 1.0 sampleset + sfx, pads and vg battles.
Also Midines allows realime pitch shifting of the sample channel via MIDI CC 03. This allows for some effects not normally possible in most .nsf files, such as rubber-band-o drums, and then back to normal in a millisecond.
The sample channel has a looping mode which can be turned off/on via MIDI CC 04. Turning on the loop mode and then using the address override routine to override the sample playback length, is an easy way to get SDM sounds (spiffy dance musy).
For glitch fanboys/girls, check out this routine.
DMC PCM Modulation (reg $4011 poke)
CC 02 = Value to load
CC 13 = Toggle OFF/ON PCM Modulation
_______________________________________________________________________________________________
____ SAMPLES + BANKING_______________________________________________________________________/\
Midines defaults to bank 01, as shown by the B1 sprite on screen in the DMC column. Bank 01 contains mostly drum samples, bank 02 contains drum samples and pads + sfx. To change banks, use MIDI CC 14.
BANK 01 = less than 64 (0x40)
BANK 02 = greater than or equal to 64 (0x40)
MIDI CC 14 Switches between Bank 01 - and Bank 02 each bank accesses 128 samples, mapped 1 to a key.
_______________________________________________________________________________________________
____ ADDRESS OVERRIDE________________________________________________________________________/\
This routine, offsets the base note sample load address. Meaning: the last note you played on the DMC channel, it can change where the sample starts playing.
Also the sample playback length is overriden, so you can scale from sharp snaps to as long as the NES hardware will allow to play.
In order to access different sounds, you will need to play different note ranges on the keyboard, because this address offset routine only offsets addresses that are in the same 16KB ROM page.
It's best just to try everything out and hit a few notes on different octaves and you'll get the idea.
Also when adjusting the address the sample channel will play back, so you can tell where your starting from, the effect is similar to AKAI samplers.
OFF = less than 64 (0x40)
ON = greater than or equal to 64 (0x40)
CC 05 = DMC Sample start address offset (Only if address override enable is ON)
CC 06 = DMC Sample sample playback length (Only if address override enable is ON)
CC 08 = Toggle OFF/ON DMC address+length override
_______________________________________________________________________________________________
____ WAVE TRAVELER__________________________________________________________________________/\
This routine loops through data on the sample channel acheiving sounds from warm basses, to garbltygook®©.
CC 09 = Travel param tone
CC 10 = Travel speed
CC 11 = Travel loop size
CC 12 = Toggle OFF/ON DMC Wave Traveler
_______________________________________________________________________________________________
______________ TROUBLE SHOOTING______________________________________________________________/\
_______________________________________________________________________________________________
________ RESET BUTTON DOES NOT RESET MIDINES________________________________________________/\
In order to completely reset Midines you need to power off the NES and then power back on. Hitting the reset button only resets the NES CPU and doesn't reset the micro inside the Midines cart.
________ BLINKING OFF/ON SCREEN_____________________________________________________________/\
This problem can be caused by either a dirty 72 pin connector, or a non NTSC-NORTH AMERICAS REGION NES being used. For more information about NES CIC and regions search online.
________ Channel Master VOLUME ___________________________________________________________/\
If MIDI CC7 (Master Volume) is at 8 or lower on the pulse or noise channels, (MIDI base channel 1,2 or 3)
Then you won't hear anything, the NES volume only has 16 levels, and 0-7 (1-8) is off.
MIDI CC7 works as a master volume, so that the individual key velocity is affected by this value.
For example if the MIDI CC7 is at half (63 or so) and you play a note with a velocity less than 64 you won't hear anything. You would have to play a note with a greater than 64 value velocity to hear anything, since the master volume is at half.
note: Many sequencers set this MIDI CC7 to a defualt value that is not %100 or 128, so you might not be getting the full volume range avaliable using velocity with Midines untill you adjust the master volume CC7 to full on.
________ PULSE OR NOISE CHANNELS STOPPED RESPONDING TO VELOCITY OR VOLUME_________________/\
This is probably because you sent MIDI CC messages to:
CC 10 = Toggle OFF/ON pulse channel loop envelope
CC 11 = Toggle OFF/ON volume Envelope disable
- The NES is a strange beast and only will respond to volume changes with these MIDI CC's set to the following:
CC10 - ON - lets the note remain looping or on
CC11 - ON - disables the hardware volume envelope, and allows the software volume, velocity routine to work.
________ GLITCHY MODE 1/2 NESFX on/off behaviour_______________________________________________/\
Old controllers can have problems where the rubber contact element disintegrates inside the controller, causing the conductive carbon to drop close to the actual switch, this makes the nes see a number of button presses even though you may be only pressing it one time.
The only remedy is to get a newer controller, or replace the parts in your original controller with the new rubber contact elements of a new controller.
________ MIDINES FREEZES____________________________________________________________________/\
If Midines stops responding to midi data it means that something went wrong with the 72 pin connector. It's best to replace the older one your probably using and get a new one.
________ MIDINES WORKS BUT EVERY SO OFTEN GETS STUCK ON OR READS BAD DATA_________________/\
If there is a grounding (earthing) problem between the NES and your MIDI Sequencer then, MIDINES can miss data unfortunatley. This occurs usually when both the NES *and* the MIDI Sequencer are using cheapo AC Adaptors.
There is a workaround but it requires a PC with a well grounded (earthed) power supply (which most are). Just run your MIDI controller into your PC's MIDI in, and then back out the PC's MIDI out, echoing the MIDI in to the out in software and Midines will work fine that way.
________ PULSE CHANNEL LOWEST OCTAVE STOPPED WORKING AFTER EDITING SWEEP SHIFT_____________/\
In order to play the lowest octave notes on the pulse channels you must make sure CC 16 = Sweep Shift, is at full on (127). Midines defaults to this setting, but if you start working around with the sweep and suddenly loose the lowest octave of a pulse channel, this is due to CC 16 Sweep Shift set lower than 127.
_______________________________________________________________________________________________
______________ SOUND TECHNIQUES______________________________________________________________/\
_______________________________________________________________________________________________
DELAY
Create a simple melody or arpeggio with the pulse channel #1 (MIDI ch1). Then copy this sequence and paste into pulse channel #2 , (MIDI ch2). Next offset the notes by an 8th note - 16th note or triplet depending on the type of delay your after and shorten or cut the remaining overhanging notes off the end of the sequence. Select all the notes on pulse channel 2 (MIDI ch2) and reduce the velocity by 10-25%.
CHORUS
A chorus sound can be achieved by playing pulse channels 1 & 2 on the same note, then using MIDI CC8 to offset one of the pulse channels pitch by a small amount. Altering the duty cycles of the pulse channels in conjunction with a slight pitch offset provides rich chorusing sounds.
FULL FREQUENCY DMC
The sample channel, while excellent for bass type sounds, has a hard time with frequencies above 8Khz or so. In order to make up for this drop in the high frequency domain, using short synchronously timed bursts of noise over the samples can together generate a full frequency sample sound. Try turning MIDI CC9 to 26 to setting the noise length, and set CC10,11 off - 0. This envelope works in a way where the greater the velocity is the longer the decay, the shorter the velocity the shorter the decay. This way it is easy to set up a high frequency layer to complement the samples.
_______________________________________________________________________________________________
______________ FAQ____________________________________________________________________________/\
_______________________________________________________________________________________________
_______________________________________________________________________________________________
____ HOW TO MAKE MIDINES WORK ON A PAL NES____________________________________________________/\
Midines 1.1.0 can operate with NTSC and PAL systems. However the CIC security chip protection limits the compatabilty. Other wise you can run Midines on a PAL NES without any issues.
The last version of the NES Nintendo made, the toploader, lacks CIC region protection. Also there are various ways to modify your old PAL NES to make it region free, you can find information on the various methods by searching online. _______________________________________________________________________________________________
____ USING MIDINES WITH FAMICOM________________________________________________________________/\
Famicom never had the CIC chip problem, so if you have a NES game to Famicom converter it will work fine.
_______________________________________________________________________________________________
____ DOES THE CABLE GET IN THE WAY?___________________________________________________________/\
No the cable sits above the lip of the NES door, so that if you really wanted to you could drill a little semi-circle out of the hood, and it would close perfectly.
_______________________________________________________________________________________________
____ CAN MIDINES RUN WITHOUT A TV?_____________________________________________________________/\
Yes, however it might be a good idea to try it out first with a TV, and get the feel for the controls, then after you have that memorized run it solo.
_______________________________________________________________________________________________
____ CAN MIDINES RUN IN AN Emulator?___________________________________________________________/\
No, the hardware (memory mapper) design has changed over time, besides there is a seperate microprocessor that does most of the MIDI processing that current NES emulators do not emulate. If you would like to make NES music on your PC check out the MCK system or NT2, a nsf tracker for dos. Also there are plenty of NES-alike vst clones around, although it's like using a SID Emulator, instead of the real thing.T]
USING MIDINES 1.1.0______________________________________________________________/\
_______________________________________________________________________________________________
_______________________________________________________________________________________________
____ USING CONTROLLER #1 ______________________________________________________________________ /\
_______________________________________________________________________________________________
____ MIDINES MODES____________________________________________________________________________/\
PRESSING SELECT ON THE #1 CONTROLLER TOGGLES BETWEEN MODES 1 and 2.
MODE 2 is the default, Mode 2 allows the screen graphics to run so that you can monitor the note sprites and also use NESFX.
MODE 1 disables the Graphics routines, which silences that nasty 60 hertz buzz, and also increases Music processing performance.
You will notice a significant sound difference between MODE 1 and MODE 2 when using things like the pulse mod hack, and the DMC Wave Traveller. So usually it's best when composing to choose the MIDI Channel offset you need and then turn Midines to Mode 1 and just keep it there for the entire composition.
_______________________________________________________________________________________________
____ MIDI CHANNEL OFFSET_______________________________________________________________________/\
PRESSING UP ON THE #1 CONTROLLER INCREMENTS THE MIDI CHANNEL OFFSET.
PRESSING DOWN ON THE #1 CONTROLLER DECREMENTS THE MIDI CHANNEL OFFSET.
NESFX must be OFF, and Midines must be in MODE 2 in order to change the MIDI Channel Offset.
-The default Midi channel assignments for Midines:
MIDI Channel 01 = Pulse 01
MIDI Channel 02 = Pulse 02
MIDI Channel 03 = Triangle
MIDI Channel 04 = Noise
MIDI Channel 05 = sample (DMC) channel
Can be changed, rather shifted - to respond to different MIDI Channels using the UP / DOWN pad on Controller #1 .
The on screen channel displays the current base channel.
This defaults to MIDI Channel 01, which will be the current MIDI Channel the Pulse 01 audio channel responds to.
If for example while Midines was in mode 2, (toggle with START button) and you pressed up twice the channel display would now read channel 03. This sets the Pulse 01 to respond to MIDI channel 03. Similarly the other audio channels will have been shifted up by 2.
-channel 03 - MIDI Channel Offset
MIDI Channel 03 = Pulse 01
MIDI Channel 04 = Pulse 02
MIDI Channel 05 = Triangle
MIDI Channel 06 = Noise
MIDI Channel 07 = DMC (sample) channel
Offset "a" is hex for decimal 10, "b" is 11.
_______________________________________________________________________________________________
____ NESFX___________________________________________________________________________________/\
Pressing START on the #1 CONTROLLER toggles NESFX ON/OFF.
Basically NESFX changes the graphics on screen based on things like channel pitch, or notes played.
_______________________________________________________________________________________________
______________ AUDIO CHANNELS + EFFECTS_______________________________________________________/\
_______________________________________________________________________________________________
The NES features 5 sound channels, 2 Pulse with 4 step variable duty cycle, and 4 bit volume control. One triangle wave channel, that unfortunately has no volume control. One noise channel with two different random waveform generation methods, a short and long loop period (same as GB). Lastly a Delta Modulation audio sample channel.
Even though Midines has a few built in ways to modulate things, the MIDI latency is low enough in mode 1 that you can modulate any parameter into the audio domain, just using your sequencer application and MIDI CC commands.
Details on each of these sound channels follow.
_______________________________________________________________________________________________
______________ PULSE CHANNELS_(MIDI 1,2)________________________________________________________/\
_______________________________________________________________________________________________
The pulse channels feature 4bit volume, 4 duty cycle settings, a sweep pitch feature, and an auto volume envelope feature. The pulse channels can also be modulated via a modulation hack that constantly resets the pulse waveform generator.
Note on velocity allows 16 volume steps, and is derived by dividing the mid note volume by 8. Therefore changes in velocity of less than 8 may not have an actual effect on the sound channels volume level. Also some sequencers do not automatically set the master volume CC7 to 127. This master volume setting must be at 127 on order to get the full volume range of velocity from the midi notes you are playing. The master volume takes precedance over velocity and scales the velocity accordingly, however remember there are only 16 steps to the volume. Therefore if the master volume CC7 is at 7 or less the channel will *not* sound at all, even when playing a note at 127 velocity.
You can use midi pitchbend to shift the pulse channel it's entire frequency, if the stepping you hear is rough it could be due to your midi controller not sending incremental midi pitchbend messages, ex. 1001,1002,1003,1004....1212,1213 these would provide a smooth pitch bend, however many keyboard controllers default to larger pitchbend increments, ex. 40, 64, 80, 128 this will cause the pitch transition to sound rough. So check your manual for a pitchbend resolution, or look to use the "fine" pitchbend for vibratos over rough. However there is way around this by using MIDI CC8, which is a fine pitch bend that runs off MIDI CC8.
Fine Pitch CC8 offsets the fine pitch register for the note only. So due to this some notes may wrap from low to high or high to low pitches.
The NES has another important hardware setting related to the avaliable frequency range of the pulse channels.
In order to play the lowest octave notes on the pulse channels you must make sure CC 16 = Sweep Shift, is at full on (127). Midines defaults to this setting, however if you start working around with the sweep and suddenly loose the lowest octave of a pulse channel, thats the reason.
PULSE MIDI CONTROLLER CHANGE MESSAGES (CC parameters)
OFF = less than 64 (0x40)
ON = greater than or equal to 64 (0x40)
Mod wheel / CC1 = Duty Cycle
CC7 = Master Volume (value overrides note velocity)
CC8 = Fine pitch mod
CC9 = Pulse channel length envelope
CC10 = Toggle OFF/ON pulse channel loop envelope
CC11 = Toggle OFF/ON volume Envelope disable
CC12 = Toggle OFF/ON Modulate pulse channel
CC13 = Toggle OFF/ON Enable Sweep
CC14 = Sweep Down / Up
CC15 = Sweep Period
CC16 = Sweep Shift
_______________________________________________________________________________________________
____ MOD HACK________________________________________________________________________________/\
MIDI CC 12 (Toggle OFF/ON) turns on the mod hack if you send a value of 64 or greater, (0x40).
MIDI CC 6 is the frequency for this routine. _______________________________________________________________________________________________
______________ TRI CHANNEL_(MIDI 3)_____________________________________________________________/\
_______________________________________________________________________________________________
The triangle channel does not support hardware volume control as do the pulse and noise channels. Despite this limitation the triangle channel features the widest frequency response that the NES has to offer.
MIDI pitchbend allows full frequency shifts.
TRIANGLE MIDI CONTROLLER CHANGE MESSAGES (CC parameters)
CC8 = Fine pitch mod
_______________________________________________________________________________________________
______________ NOISE CHANNEL_(MIDI 4)___________________________________________________________/\
_______________________________________________________________________________________________
The noise sound channel features 4bit volume control, and also has an auto volume envelope feature, similar to the pulse channels. The noise channel has 2 modes of noise generation, long loop and short loop.
Long mode allows for standard noise generation, and short mode sounds more metallic and less random, more periodic. The NES's long / short noise loop modes are similar to the Game Boy noise modes.
The noise channel is spread out over MIDI channel 4. Due to the limited 16 noise pitch/period values that the NES allows, the noise period is repeated every 16 notes. For MIDI notes above 64 inclusive (64 dec 40 hex), noise short loop mode is set to on. For MIDI notes below 64 (64 dec 40 hex) the long mode is on.
Note on velocity allows 16 volume steps, and is derived by dividing the midi note volume by 8, scaled by the master volume. Therefore changes in velocity of less than 8 may not have an actual effect on the sound channels volume level.
NOISE MIDI CONTROLLER CHANGE MESSAGES (CC parameters)
OFF = less than 64 (0x40)
ON = greater than or equal to 64 (0x40)
CC7 = Master Volume
CC9 = Noise channel length envelope
CC10 = Toggle OFF/ON noise channel loop envelope
CC11 = Toggle OFF/ON volume Envelope disable
_______________________________________________________________________________________________
______________ SAMPLE CHANNEL (DMC)_(MIDI 5)____________________________________________________/\
_______________________________________________________________________________________________
The sample channel in Midines 1.1.0 features 256 different samples grouped into two 128 note sound banks. Samplesets include, TR909, TR808, TR707, LINN, AMEN, VG, HONG KONG BATTLE ACTION!, as well as additional breaks, and the older 1.0 sampleset + sfx, pads and vg battles.
Also Midines allows realime pitch shifting of the sample channel via MIDI CC 03. This allows for some effects not normally possible in most .nsf files, such as rubber-band-o drums, and then back to normal in a millisecond.
The sample channel has a looping mode which can be turned off/on via MIDI CC 04. Turning on the loop mode and then using the address override routine to override the sample playback length, is an easy way to get SDM sounds (spiffy dance musy).
For glitch fanboys/girls, check out this routine.
DMC PCM Modulation (reg $4011 poke)
CC 02 = Value to load
CC 13 = Toggle OFF/ON PCM Modulation
_______________________________________________________________________________________________
____ SAMPLES + BANKING_______________________________________________________________________/\
Midines defaults to bank 01, as shown by the B1 sprite on screen in the DMC column. Bank 01 contains mostly drum samples, bank 02 contains drum samples and pads + sfx. To change banks, use MIDI CC 14.
BANK 01 = less than 64 (0x40)
BANK 02 = greater than or equal to 64 (0x40)
MIDI CC 14 Switches between Bank 01 - and Bank 02 each bank accesses 128 samples, mapped 1 to a key.
_______________________________________________________________________________________________
____ ADDRESS OVERRIDE________________________________________________________________________/\
This routine, offsets the base note sample load address. Meaning: the last note you played on the DMC channel, it can change where the sample starts playing.
Also the sample playback length is overriden, so you can scale from sharp snaps to as long as the NES hardware will allow to play.
In order to access different sounds, you will need to play different note ranges on the keyboard, because this address offset routine only offsets addresses that are in the same 16KB ROM page.
It's best just to try everything out and hit a few notes on different octaves and you'll get the idea.
Also when adjusting the address the sample channel will play back, so you can tell where your starting from, the effect is similar to AKAI samplers.
OFF = less than 64 (0x40)
ON = greater than or equal to 64 (0x40)
CC 05 = DMC Sample start address offset (Only if address override enable is ON)
CC 06 = DMC Sample sample playback length (Only if address override enable is ON)
CC 08 = Toggle OFF/ON DMC address+length override
_______________________________________________________________________________________________
____ WAVE TRAVELER__________________________________________________________________________/\
This routine loops through data on the sample channel acheiving sounds from warm basses, to garbltygook®©.
CC 09 = Travel param tone
CC 10 = Travel speed
CC 11 = Travel loop size
CC 12 = Toggle OFF/ON DMC Wave Traveler
_______________________________________________________________________________________________
______________ TROUBLE SHOOTING______________________________________________________________/\
_______________________________________________________________________________________________
________ RESET BUTTON DOES NOT RESET MIDINES________________________________________________/\
In order to completely reset Midines you need to power off the NES and then power back on. Hitting the reset button only resets the NES CPU and doesn't reset the micro inside the Midines cart.
________ BLINKING OFF/ON SCREEN_____________________________________________________________/\
This problem can be caused by either a dirty 72 pin connector, or a non NTSC-NORTH AMERICAS REGION NES being used. For more information about NES CIC and regions search online.
________ Channel Master VOLUME ___________________________________________________________/\
If MIDI CC7 (Master Volume) is at 8 or lower on the pulse or noise channels, (MIDI base channel 1,2 or 3)
Then you won't hear anything, the NES volume only has 16 levels, and 0-7 (1-8) is off.
MIDI CC7 works as a master volume, so that the individual key velocity is affected by this value.
For example if the MIDI CC7 is at half (63 or so) and you play a note with a velocity less than 64 you won't hear anything. You would have to play a note with a greater than 64 value velocity to hear anything, since the master volume is at half.
note: Many sequencers set this MIDI CC7 to a defualt value that is not %100 or 128, so you might not be getting the full volume range avaliable using velocity with Midines untill you adjust the master volume CC7 to full on.
________ PULSE OR NOISE CHANNELS STOPPED RESPONDING TO VELOCITY OR VOLUME_________________/\
This is probably because you sent MIDI CC messages to:
CC 10 = Toggle OFF/ON pulse channel loop envelope
CC 11 = Toggle OFF/ON volume Envelope disable
- The NES is a strange beast and only will respond to volume changes with these MIDI CC's set to the following:
CC10 - ON - lets the note remain looping or on
CC11 - ON - disables the hardware volume envelope, and allows the software volume, velocity routine to work.
________ GLITCHY MODE 1/2 NESFX on/off behaviour_______________________________________________/\
Old controllers can have problems where the rubber contact element disintegrates inside the controller, causing the conductive carbon to drop close to the actual switch, this makes the nes see a number of button presses even though you may be only pressing it one time.
The only remedy is to get a newer controller, or replace the parts in your original controller with the new rubber contact elements of a new controller.
________ MIDINES FREEZES____________________________________________________________________/\
If Midines stops responding to midi data it means that something went wrong with the 72 pin connector. It's best to replace the older one your probably using and get a new one.
________ MIDINES WORKS BUT EVERY SO OFTEN GETS STUCK ON OR READS BAD DATA_________________/\
If there is a grounding (earthing) problem between the NES and your MIDI Sequencer then, MIDINES can miss data unfortunatley. This occurs usually when both the NES *and* the MIDI Sequencer are using cheapo AC Adaptors.
There is a workaround but it requires a PC with a well grounded (earthed) power supply (which most are). Just run your MIDI controller into your PC's MIDI in, and then back out the PC's MIDI out, echoing the MIDI in to the out in software and Midines will work fine that way.
________ PULSE CHANNEL LOWEST OCTAVE STOPPED WORKING AFTER EDITING SWEEP SHIFT_____________/\
In order to play the lowest octave notes on the pulse channels you must make sure CC 16 = Sweep Shift, is at full on (127). Midines defaults to this setting, but if you start working around with the sweep and suddenly loose the lowest octave of a pulse channel, this is due to CC 16 Sweep Shift set lower than 127.
_______________________________________________________________________________________________
______________ SOUND TECHNIQUES______________________________________________________________/\
_______________________________________________________________________________________________
DELAY
Create a simple melody or arpeggio with the pulse channel #1 (MIDI ch1). Then copy this sequence and paste into pulse channel #2 , (MIDI ch2). Next offset the notes by an 8th note - 16th note or triplet depending on the type of delay your after and shorten or cut the remaining overhanging notes off the end of the sequence. Select all the notes on pulse channel 2 (MIDI ch2) and reduce the velocity by 10-25%.
CHORUS
A chorus sound can be achieved by playing pulse channels 1 & 2 on the same note, then using MIDI CC8 to offset one of the pulse channels pitch by a small amount. Altering the duty cycles of the pulse channels in conjunction with a slight pitch offset provides rich chorusing sounds.
FULL FREQUENCY DMC
The sample channel, while excellent for bass type sounds, has a hard time with frequencies above 8Khz or so. In order to make up for this drop in the high frequency domain, using short synchronously timed bursts of noise over the samples can together generate a full frequency sample sound. Try turning MIDI CC9 to 26 to setting the noise length, and set CC10,11 off - 0. This envelope works in a way where the greater the velocity is the longer the decay, the shorter the velocity the shorter the decay. This way it is easy to set up a high frequency layer to complement the samples.
_______________________________________________________________________________________________
______________ FAQ____________________________________________________________________________/\
_______________________________________________________________________________________________
_______________________________________________________________________________________________
____ HOW TO MAKE MIDINES WORK ON A PAL NES____________________________________________________/\
Midines 1.1.0 can operate with NTSC and PAL systems. However the CIC security chip protection limits the compatabilty. Other wise you can run Midines on a PAL NES without any issues.
The last version of the NES Nintendo made, the toploader, lacks CIC region protection. Also there are various ways to modify your old PAL NES to make it region free, you can find information on the various methods by searching online. _______________________________________________________________________________________________
____ USING MIDINES WITH FAMICOM________________________________________________________________/\
Famicom never had the CIC chip problem, so if you have a NES game to Famicom converter it will work fine.
_______________________________________________________________________________________________
____ DOES THE CABLE GET IN THE WAY?___________________________________________________________/\
No the cable sits above the lip of the NES door, so that if you really wanted to you could drill a little semi-circle out of the hood, and it would close perfectly.
_______________________________________________________________________________________________
____ CAN MIDINES RUN WITHOUT A TV?_____________________________________________________________/\
Yes, however it might be a good idea to try it out first with a TV, and get the feel for the controls, then after you have that memorized run it solo.
_______________________________________________________________________________________________
____ CAN MIDINES RUN IN AN Emulator?___________________________________________________________/\
No, the hardware (memory mapper) design has changed over time, besides there is a seperate microprocessor that does most of the MIDI processing that current NES emulators do not emulate. If you would like to make NES music on your PC check out the MCK system or NT2, a nsf tracker for dos. Also there are plenty of NES-alike vst clones around, although it's like using a SID Emulator, instead of the real thing.T]
TEK E7 electronique analogique, studio & sound system
TekE7
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Posteur·euse AFfamé·e
Membre depuis 20 ans
5 Posté le 22/12/2022 à 11:55:08
Pour allez plus loin: https://www.nesdev.org/apu_ref.txt
NES APU Sound Hardware Reference
--------------------------------
This reference covers Nintendo Entertainment System (NES) sound hardware in as
much detail as I know. It is intended primarily to assist in the implementation
of emulators and might also be useful as a programmer reference.
Tables, diagrams, and formulas are formatted for a mono-spaced font, like
Courier.
The latest version is kept at http://www.slack.net/~ant/nes-emu/apu_ref.txt
-----
Intro
-----
This reference is based on the results of tests I have run on a 1988-model US
NTSC NES which contains the G revision of the 2A03 CPU/APU and the NES-CPU-07
version of the main board. PAL hardware will be covered once tests are
performed on it. Feel free to incorporate this information in references and
other documentation.
While implementing a NES sound emulator, even after reading the available
documentation I still had many unanswered questions, so I made a simple
development cartridge to test on a real NES. This was very successful and
revealed many new details. My notes consisted of differences from existing
documentation, but this didn't seem to be a very reliable way to release my
findings, so I decided to write a concise reference.
For those familiar with NESSOUND.TXT and DMC.TXT, the following differences
should be specifically noted:
Corrections:
- DMC table entry $D should be $2A0 instead of $2A8
- Frame sequencer
- Square's duty generator
Clarifications:
- DMC
- Triangle's linear counter
- Length Counter operation and status register behavior
It should go without saying that the model presented here probably doesn't
match the actual logic gate arrangement in the NES. It makes no difference how
the hardware is implemented, as long as its behavior matches what is described
here
Corrections, questions and additions are welcome. I keep up with the forum at
http://nesdev.parodius.com/ and can be contacted via blargg at the mail.com
domain.
-----
To Do
-----
- See if comprehensive emulator test ROM is even practical.
- Probe complete power-up state and reset state.
- Test PAL hardware to determine APU frame rate, DMC and noise period tables.
- Check complete behavior of each unit of each channel to be sure common units
behave the same for all channels.
- Double-check details on NES hardware again.
- Determine post-DAC filtering done before output.
--------
Overview
--------
The APU is composed of five channels: square 1, square 2, triangle, noise,
delta modulation channel (DMC). Each has a variable-rate timer clocking a
waveform generator, and various modulators driven by low-frequency clocks from
a frame sequencer. The DMC plays samples while the other channels play
waveforms. The waveform channels have duration control, some have a volume
envelope unit, and a couple have a frequency sweep unit.
Square 1/Square 2
$4000/4 ddle nnnn duty, loop env/disable length, env disable, vol/env
period
$4001/5 eppp nsss enable sweep, period, negative, shift
$4002/6 pppp pppp period low
$4003/7 llll lppp length index, period high
Triangle
$4008 clll llll control, linear counter load
$400A pppp pppp period low
$400B llll lppp length index, period high
Noise
$400C --le nnnn loop env/disable length, env disable, vol/env period
$400E s--- pppp short mode, period index
$400F llll l--- length index
DMC
$4010 il-- ffff IRQ enable, loop, frequency index
$4011 -ddd dddd DAC
$4012 aaaa aaaa sample address
$4013 llll llll sample length
Common
$4015 ---d nt21 length ctr enable: DMC, noise, triangle, pulse 2, 1
$4017 fd-- ---- 5-frame cycle, disable frame interrupt
Status (read)
$4015 if-d nt21 DMC IRQ, frame IRQ, length counter statuses
------
Basics
------
Hexadecimal values are prefixed by a $ except for some single-hex-digit
sequences where it's clear that they are hex. Bits are numbered from 0 to 7,
corresponding with the least to most significant bits of a byte; bit n has a
binary weight of 2^n.
A flag is a two-state variable that can be either set or clear. When
implemented in a bit, clear = 0 and set = 1.
A divider outputs a clock every n input clocks, where n is the divider's
period. It contains a counter which is decremented on the arrival of each
clock. When it reaches 0, it is reloaded with the period and an output clock is
generated. Resetting a divider reloads its counter without generating an output
clock. Changing a divider's period doesn't affect its current count.
A sequencer generates a series of values or events based on the repetition of a
series of steps, starting with the first. When clocked the next step of the
sequence is generated.
In the block diagrams, the triangular symbol is a control gate; if control is
non-zero, the input is passed unchanged to the output, otherwise the output is
0.
control
|
v
|\
in -->| >-- out
|/
Except for the status register, all other registers are write-only. The "value
of the register" refers to the last value written to the register.
The NTSC NES has a master clock based on a 21.47727 MHz crystal which is
divided by 12 to obtain a ~1.79 MHz clock source. Both clocks are used by the
APU.
The CPU's IRQ line is level-sensitive, so the APU's interrupt flags must be
cleared once a CPU IRQ is acknowledged, otherwise the CPU will immediately be
interrupt again once its inhibit flag is cleared.
In general, the APU is a collection of many independent units which are always
running in parallel. Modification of a channel's parameter usually affects only
one sub-unit and doesn't take effect until that unit's next internal cycle
begins.
Each section begins with an overview and an optional block diagram, which
provide a framework for the information that follows. In order to reduce
ambiguity, there is very little re-statement of information.
---------------
Frame Sequencer
---------------
The frame sequencer contains a divider and a sequencer which clocks various
units.
The divider generates an output clock rate of just under 240 Hz, and appears to
be derived by dividing the 21.47727 MHz system clock by 89490. The sequencer is
clocked by the divider's output.
On a write to $4017, the divider and sequencer are reset, then the sequencer is
configured. Two sequences are available, and frame IRQ generation can be
disabled.
mi-- ---- mode, IRQ disable
If the mode flag is clear, the 4-step sequence is selected, otherwise the
5-step sequence is selected and the sequencer is immediately clocked once.
f = set interrupt flag
l = clock length counters and sweep units
e = clock envelopes and triangle's linear counter
mode 0: 4-step effective rate (approx)
---------------------------------------
- - - f 60 Hz
- l - l 120 Hz
e e e e 240 Hz
mode 1: 5-step effective rate (approx)
---------------------------------------
- - - - - (interrupt flag never set)
l - l - - 96 Hz
e e e e - 192 Hz
At any time if the interrupt flag is set and the IRQ disable is clear, the
CPU's IRQ line is asserted.
--------------
Length Counter
--------------
A length counter allows automatic duration control. Counting can be halted and
the counter can be disabled by clearing the appropriate bit in the status
register, which immediately sets the counter to 0 and keeps it there.
The halt flag is in the channel's first register. For the square and noise
channels, it is bit 5, and for the triangle, bit 7:
--h- ---- halt (noise and square channels)
h--- ---- halt (triangle channel)
Note that the bit position for the halt flag is also mapped to another flag in
the Length Counter (noise and square) or Linear Counter (triangle).
Unless disabled, a write the channel's fourth register immediately reloads the
counter with the value from a lookup table, based on the index formed by the
upper 5 bits:
iiii i--- length index
bits bit 3
7-4 0 1
-------
0 $0A $FE
1 $14 $02
2 $28 $04
3 $50 $06
4 $A0 $08
5 $3C $0A
6 $0E $0C
7 $1A $0E
8 $0C $10
9 $18 $12
A $30 $14
B $60 $16
C $C0 $18
D $48 $1A
E $10 $1C
F $20 $1E
See the clarifications section for a possible explanation for the values left
column of the table.
When clocked by the frame sequencer, if the halt flag is clear and the counter
is non-zero, it is decremented.
---------------
Status Register
---------------
The status register at $4015 allows control and query of the channels' length
counters, and query of the DMC and frame interrupts. It is the only register
which can also be read.
When $4015 is read, the status of the channels' length counters and bytes
remaining in the current DMC sample, and interrupt flags are returned.
Afterwards the Frame Sequencer's frame interrupt flag is cleared.
if-d nt21
IRQ from DMC
frame interrupt
DMC sample bytes remaining > 0
triangle length counter > 0
square 2 length counter > 0
square 1 length counter > 0
When $4015 is written to, the channels' length counter enable flags are set,
the DMC is possibly started or stopped, and the DMC's IRQ occurred flag is
cleared.
---d nt21 DMC, noise, triangle, square 2, square 1
If d is set and the DMC's DMA reader has no more sample bytes to fetch, the DMC
sample is restarted. If d is clear then the DMA reader's sample bytes remaining
is set to 0.
------------------
Envelope Generator
------------------
An envelope generator can generate a constant volume or a saw envelope with
optional looping. It contains a divider and a counter.
A channel's first register controls the envelope:
--ld nnnn loop, disable, n
Note that the bit position for the loop flag is also mapped to a flag in the
Length Counter.
The divider's period is set to n + 1.
When clocked by the frame sequencer, one of two actions occurs: if there was a
write to the fourth channel register since the last clock, the counter is set
to 15 and the divider is reset, otherwise the divider is clocked.
When the divider outputs a clock, one of two actions occurs: if loop is set and
counter is zero, it is set to 15, otherwise if counter is non-zero, it is
decremented.
When disable is set, the channel's volume is n, otherwise it is the value in
the counter. Unless overridden by some other condition, the channel's DAC
receives the channel's volume value.
-----
Timer
-----
All channels use a timer which is a divider driven by the ~1.79 MHz clock.
The noise channel and DMC use lookup tables to set the timer's period. For the
square and triangle channels, the third and fourth registers form an 11-bit
value and the divider's period is set to this value *plus one*.
llll llll low 8 bits of period (third register)
---- -hhh upper 3 bits of period (fourth register)
----------
Sweep Unit
----------
The sweep unit can adjust a square channel's period periodically. It contains a
divider and a shifter.
A channel's second register configures the sweep unit:
eppp nsss enable, period, negate, shift
The divider's period is set to p + 1.
The shifter continuously calculates a result based on the channel's period. The
channel's period (from the third and fourth registers) is first shifted right
by s bits. If negate is set, the shifted value's bits are inverted, and on the
second square channel, the inverted value is incremented by 1. The resulting
value is added with the channel's current period, yielding the final result.
When the sweep unit is clocked, the divider is *first* clocked and then if
there was a write to the sweep register since the last sweep clock, the divider
is reset.
When the channel's period is less than 8 or the result of the shifter is
greater than $7FF, the channel's DAC receives 0 and the sweep unit doesn't
change the channel's period. Otherwise, if the sweep unit is enabled and the
shift count is greater than 0, when the divider outputs a clock, the channel's
period in the third and fourth registers are updated with the result of the
shifter.
--------------
Square Channel
--------------
+---------+ +---------+
| Sweep |--->|Timer / 2|
+---------+ +---------+
| |
| v
| +---------+ +---------+
| |Sequencer| | Length |
| +---------+ +---------+
| | |
v v v
+---------+ |\ |\ |\ +---------+
|Envelope |------->| >----------->| >----------->| >-------->| DAC |
+---------+ |/ |/ |/ +---------+
There are two square channels beginning at registers $4000 and $4004. Each
contains the following: Envelope Generator, Sweep Unit, Timer with
divide-by-two on the output, 8-step sequencer, Length Counter.
$4000/$4004: duty, envelope
$4001/$4005: sweep unit
$4002/$4006: period low
$4003/$4007: reload length counter, period high
In addition to the envelope, the first register controls the duty cycle of the
square wave, without resetting the position of the sequencer:
dd-- ---- duty cycle select
d waveform sequence
---------------------
_ 1
0 - ------ 0 (12.5%)
__ 1
1 - ----- 0 (25%)
____ 1
2 - --- 0 (50%)
_ _____ 1
3 -- 0 (25% negated)
When the fourth register is written to, the sequencer is restarted.
The sequencer is clocked by the divided timer output.
When the sequencer output is low, the DAC receives 0.
--------------
Linear Counter
--------------
The Linear Counter serves as a second more-accurate duration counter for the
triangle channel. It contains a counter and an internal halt flag.
Register $4008 contains a control flag and reload value:
crrr rrrr control flag, reload value
Note that the bit position for the control flag is also mapped to a flag in the
Length Counter.
When register $400B is written to, the halt flag is set.
When clocked by the frame sequencer, the following actions occur in order:
1) If halt flag is set, set counter to reload value, otherwise if counter
is non-zero, decrement it.
2) If control flag is clear, clear halt flag.
----------------
Triangle Channel
----------------
+---------+ +---------+
|LinearCtr| | Length |
+---------+ +---------+
| |
v v
+---------+ |\ |\ +---------+ +---------+
| Timer |------->| >----------->| >------->|Sequencer|--->| DAC |
+---------+ |/ |/ +---------+ +---------+
The triangle channel contains the following: Timer, 32-step sequencer, Length
Counter, Linear Counter, 4-bit DAC.
$4008: length counter disable, linear counter
$400A: period low
$400B: length counter reload, period high
When the timer generates a clock and the Length Counter and Linear Counter both
have a non-zero count, the sequencer is clocked.
The sequencer feeds the following repeating 32-step sequence to the DAC:
F E D C B A 9 8 7 6 5 4 3 2 1 0 0 1 2 3 4 5 6 7 8 9 A B C D E F
At the lowest two periods ($400B = 0 and $400A = 0 or 1), the resulting
frequency is so high that the DAC effectively outputs a value half way between
7 and 8.
-------------
Noise Channel
-------------
+---------+ +---------+ +---------+
| Timer |--->| Random | | Length |
+---------+ +---------+ +---------+
| |
v v
+---------+ |\ |\ +---------+
|Envelope |------->| >----------->| >------->| DAC |
+---------+ |/ |/ +---------+
The noise channel starts at register $400C and contains the following: Length
Counter, Envelope Generator, Timer, 15-bit right shift register with feedback,
4-bit DAC.
$400C: envelope
$400E: mode, period
$400F: reload length counter
Register $400E sets the random generator mode and timer period based on a 4-bit
index into a period table:
m--- iiii mode, period index
i timer period
----------------
0 $004
1 $008
2 $010
3 $020
4 $040
5 $060
6 $080
7 $0A0
8 $0CA
9 $0FE
A $17C
B $1FC
C $2FA
D $3F8
E $7F2
F $FE4
The shift register is clocked by the timer and the vacated bit 14 is filled
with the exclusive-OR of *pre-shifted* bits 0 and 1 (mode = 0) or bits 0 and 6
(mode = 1), resulting in 32767-bit and 93-bit sequences, respectively.
When bit 0 of the shift register is set, the DAC receives 0.
On power-up, the shift register is loaded with the value 1.
------------------------------
Delta Modulation Channel (DMC)
------------------------------
+----------+ +---------+
|DMA Reader| | Timer |
+----------+ +---------+
| |
| v
+----------+ +---------+ +---------+ +---------+
| Buffer |----| Output |---->| Counter |---->| DAC |
+----------+ +---------+ +---------+ +---------+
The DMC can output samples composed of 1-bit deltas and its DAC can be directly
changed. It contains the following: DMA reader, interrupt flag, sample buffer,
Timer, output unit, 7-bit counter tied to 7-bit DAC.
$4010: mode, frequency
$4011: DAC
$4012: address
$4013: length
On power-up, the DAC counter contains 0.
Register $4010 sets the interrupt enable, loop, and timer period. If the new
interrupt enabled status is clear, the interrupt flag is cleared.
il-- ffff interrupt enabled, loop, frequency index
f period
----------
0 $1AC
1 $17C
2 $154
3 $140
4 $11E
5 $0FE
6 $0E2
7 $0D6
8 $0BE
9 $0A0
A $08E
B $080
C $06A
D $054
E $048
F $036
A write to $4011 sets the counter and DAC to a new value:
-ddd dddd new DAC value
Sample Buffer
-------------
The sample buffer either holds a single sample byte or is empty. It is filled
by the DMA reader and can only be emptied by the output unit, so once loaded
with a sample it will be eventually output.
DMA Reader
----------
The DMA reader fills the sample buffer with successive bytes from the current
sample, whenever it becomes empty. It has an address counter and a bytes remain
counter.
When the DMC sample is restarted, the address counter is set to register $4012
* $40 + $C000 and the bytes counter is set to register $4013 * $10 + 1.
When the sample buffer is in an empty state and the bytes counter is non-zero,
the following occur: The sample buffer is filled with the next sample byte read
from memory at the current address, subject to whatever mapping hardware is
present (the same as CPU memory accesses). The address is incremented; if it
exceeds $FFFF, it is wrapped around to $8000. The bytes counter is decremented;
if it becomes zero and the loop flag is set, the sample is restarted (see
above), otherwise if the bytes counter becomes zero and the interrupt enabled
flag is set, the interrupt flag is set.
When the DMA reader accesses a byte of memory, the CPU is suspended for 4 clock
cycles.
Output Unit
-----------
The output unit continually outputs complete sample bytes or silences of equal
duration. It contains an 8-bit right shift register, a counter, and a silence
flag.
When an output cycle is started, the counter is loaded with 8 and if the sample
buffer is empty, the silence flag is set, otherwise the silence flag is cleared
and the sample buffer is emptied into the shift register.
On the arrival of a clock from the timer, the following actions occur in order:
1. If the silence flag is clear, bit 0 of the shift register is applied to
the DAC counter: If bit 0 is clear and the counter is greater than 1, the
counter is decremented by 2, otherwise if bit 0 is set and the counter is less
than 126, the counter is incremented by 2.
1) The shift register is clocked.
2) The counter is decremented. If it becomes zero, a new cycle is started.
----------
DAC Output
----------
The DACs for each channel are implemented in a way that causes non-linearity
and interaction between channels, so calculation of the resulting amplitude is
somewhat involved.
The normalized audio output level is the sum of two groups of channels:
output = square_out + tnd_out
95.88
square_out = -----------------------
8128
----------------- + 100
square1 + square2
159.79
tnd_out = ------------------------------
1
------------------------ + 100
triangle noise dmc
-------- + ----- + -----
8227 12241 22638
where triangle, noise, dmc, square1 and square2 are the values fed to their
DACs. The dmc ranges from 0 to 127 and the others range from 0 to 15. When the
sub-denominator of a group is zero, its output is 0. The output ranges from 0.0
to 1.0.
Implementation Using Lookup Table
---------------------------------
The formulas can be efficiently implemented using two lookup tables: a 31-entry
table for the two square channels and a 203-entry table for the remaining
channels (due to the approximation of tnd_out, the numerators are adjusted
slightly to preserve the normalized output range).
square_table [n] = 95.52 / (8128.0 / n + 100)
square_out = square_table [square1 + square2]
The latter table is approximated (within 4%) by using a base unit close to the
DMC's DAC.
tnd_table [n] = 163.67 / (24329.0 / n + 100)
tnd_out = tnd_table [3 * triangle + 2 * noise + dmc]
Linear Approximation
--------------------
A linear approximation can also be used, which results in slightly louder DMC
samples, but otherwise fairly accurate operation since the wave channels use a
small portion of the transfer curve. The overall volume will be reduced due to
the headroom required by the DMC approximation.
square_out = 0.00752 * (square1 + square2)
tnd_out = 0.00851 * triangle + 0.00494 * noise + 0.00335 * dmc
This linear approximation neglects the attenuating effect the DMC has when its
DAC is in the upper level. This factor can be calculated using the main formula
to form a ratio, and precalculated into a 128-entry lookup table.
tnd_out(triangle=15,dmc=d) - tnd_out(triangle=0,dmc=d)
attenuation(d) = ------------------------------------------------------
tnd_out(triangle=15,dmc=0)
-------------------
Unreliable Behavior
-------------------
(The following behaviors probably don't need to be emulated due to their
unreliability since stable code will avoid invoking it, and since their
behavior is somewhat difficult to precisely predict.)
If the frame IRQ is set just as register $4015 is being read, it seems to be
ignored (similar to polling $2002 for the vbl flag).
The DMC's DMA reader seems to check for an empty buffer every few CPU cycles,
rather than every cycle or continuously.
Writing to the DAC register ($4011) while a sample is playing sometimes has no
effect, probably because the DMC's output unit is clocking the counter at the
same moment as the write.
--------------
Clarifications
--------------
(The following are meant only as re-statements of the main content, rather than
additions of new content.)
Because the envelope loop and length counter disable flags are mapped to the
same bit, the length counter can't be used while the envelope is in loop mode.
Similar applies to the triangle channel, where the linear counter and length
counter are both controlled by the same bit in register $4008.
Unlike the other waveform channels, the triangle channel is silenced by
stopping its waveform at whatever phase it's at, rather than causing zero to be
sent to its DAC.
The length counter table seems to be set up for standard note durations for 4/4
time at 160 bpm and 180 bpm. If bit 3 is 0, the following results (Dn is bit n
of the fourth channel register):
180bpm 160bpm
D6-D4 D7=0 D7=1 note
-------------------------------
$00 10 12 16th
$01 20 24 8th
$02 40 48 4th (one beat)
$03 80 96 half
$04 160 192 whole
$05 60 72 4th dotted
$06 14 16 8th triplet (*3 = a 4th)
$07 26 32 4th triplet (*3 = a half)
-------------
Collaborators
-------------
Brad Taylor's NESSOUND.TXT and DMC.TXT as a starting point for testing.
NTSC NES for testing on.
Nesdev forum for feedback.
xodnizel for testing results, correction to DMC table, feedback.
Bloopaws/Draci for feedback, possible explanation of length counter table
values.
-------
History
-------
2003.12.01
Made development cartridge and started testing on NES hardware.
2003.12.14
Started project.
2003.12.20
A few draft sections were posted to Nesdev or e-mailed privately.
2004.01.02
Draft version posted to Nesdev. Corrected tnd_table formula.
2004.01.02
Corrected incorrect "correction" to tnd_table formula. Double-checked them.
2004.01.03
Corrected envelope flag name to "disable" (it was named "enable").
Added effective frequencies of frame sequencer outputs.
Added Overview, Unreliable Behavior, Clarifications, and Collaborators
sections.
2004.01.04
Adjusted linear approximation (difficult to find a compromise).
A few minor edits.
2004.01.30
First release. Probably won't be doing much with it for a while.
NES APU Sound Hardware Reference
--------------------------------
This reference covers Nintendo Entertainment System (NES) sound hardware in as
much detail as I know. It is intended primarily to assist in the implementation
of emulators and might also be useful as a programmer reference.
Tables, diagrams, and formulas are formatted for a mono-spaced font, like
Courier.
The latest version is kept at http://www.slack.net/~ant/nes-emu/apu_ref.txt
-----
Intro
-----
This reference is based on the results of tests I have run on a 1988-model US
NTSC NES which contains the G revision of the 2A03 CPU/APU and the NES-CPU-07
version of the main board. PAL hardware will be covered once tests are
performed on it. Feel free to incorporate this information in references and
other documentation.
While implementing a NES sound emulator, even after reading the available
documentation I still had many unanswered questions, so I made a simple
development cartridge to test on a real NES. This was very successful and
revealed many new details. My notes consisted of differences from existing
documentation, but this didn't seem to be a very reliable way to release my
findings, so I decided to write a concise reference.
For those familiar with NESSOUND.TXT and DMC.TXT, the following differences
should be specifically noted:
Corrections:
- DMC table entry $D should be $2A0 instead of $2A8
- Frame sequencer
- Square's duty generator
Clarifications:
- DMC
- Triangle's linear counter
- Length Counter operation and status register behavior
It should go without saying that the model presented here probably doesn't
match the actual logic gate arrangement in the NES. It makes no difference how
the hardware is implemented, as long as its behavior matches what is described
here
Corrections, questions and additions are welcome. I keep up with the forum at
http://nesdev.parodius.com/ and can be contacted via blargg at the mail.com
domain.
-----
To Do
-----
- See if comprehensive emulator test ROM is even practical.
- Probe complete power-up state and reset state.
- Test PAL hardware to determine APU frame rate, DMC and noise period tables.
- Check complete behavior of each unit of each channel to be sure common units
behave the same for all channels.
- Double-check details on NES hardware again.
- Determine post-DAC filtering done before output.
--------
Overview
--------
The APU is composed of five channels: square 1, square 2, triangle, noise,
delta modulation channel (DMC). Each has a variable-rate timer clocking a
waveform generator, and various modulators driven by low-frequency clocks from
a frame sequencer. The DMC plays samples while the other channels play
waveforms. The waveform channels have duration control, some have a volume
envelope unit, and a couple have a frequency sweep unit.
Square 1/Square 2
$4000/4 ddle nnnn duty, loop env/disable length, env disable, vol/env
period
$4001/5 eppp nsss enable sweep, period, negative, shift
$4002/6 pppp pppp period low
$4003/7 llll lppp length index, period high
Triangle
$4008 clll llll control, linear counter load
$400A pppp pppp period low
$400B llll lppp length index, period high
Noise
$400C --le nnnn loop env/disable length, env disable, vol/env period
$400E s--- pppp short mode, period index
$400F llll l--- length index
DMC
$4010 il-- ffff IRQ enable, loop, frequency index
$4011 -ddd dddd DAC
$4012 aaaa aaaa sample address
$4013 llll llll sample length
Common
$4015 ---d nt21 length ctr enable: DMC, noise, triangle, pulse 2, 1
$4017 fd-- ---- 5-frame cycle, disable frame interrupt
Status (read)
$4015 if-d nt21 DMC IRQ, frame IRQ, length counter statuses
------
Basics
------
Hexadecimal values are prefixed by a $ except for some single-hex-digit
sequences where it's clear that they are hex. Bits are numbered from 0 to 7,
corresponding with the least to most significant bits of a byte; bit n has a
binary weight of 2^n.
A flag is a two-state variable that can be either set or clear. When
implemented in a bit, clear = 0 and set = 1.
A divider outputs a clock every n input clocks, where n is the divider's
period. It contains a counter which is decremented on the arrival of each
clock. When it reaches 0, it is reloaded with the period and an output clock is
generated. Resetting a divider reloads its counter without generating an output
clock. Changing a divider's period doesn't affect its current count.
A sequencer generates a series of values or events based on the repetition of a
series of steps, starting with the first. When clocked the next step of the
sequence is generated.
In the block diagrams, the triangular symbol is a control gate; if control is
non-zero, the input is passed unchanged to the output, otherwise the output is
0.
control
|
v
|\
in -->| >-- out
|/
Except for the status register, all other registers are write-only. The "value
of the register" refers to the last value written to the register.
The NTSC NES has a master clock based on a 21.47727 MHz crystal which is
divided by 12 to obtain a ~1.79 MHz clock source. Both clocks are used by the
APU.
The CPU's IRQ line is level-sensitive, so the APU's interrupt flags must be
cleared once a CPU IRQ is acknowledged, otherwise the CPU will immediately be
interrupt again once its inhibit flag is cleared.
In general, the APU is a collection of many independent units which are always
running in parallel. Modification of a channel's parameter usually affects only
one sub-unit and doesn't take effect until that unit's next internal cycle
begins.
Each section begins with an overview and an optional block diagram, which
provide a framework for the information that follows. In order to reduce
ambiguity, there is very little re-statement of information.
---------------
Frame Sequencer
---------------
The frame sequencer contains a divider and a sequencer which clocks various
units.
The divider generates an output clock rate of just under 240 Hz, and appears to
be derived by dividing the 21.47727 MHz system clock by 89490. The sequencer is
clocked by the divider's output.
On a write to $4017, the divider and sequencer are reset, then the sequencer is
configured. Two sequences are available, and frame IRQ generation can be
disabled.
mi-- ---- mode, IRQ disable
If the mode flag is clear, the 4-step sequence is selected, otherwise the
5-step sequence is selected and the sequencer is immediately clocked once.
f = set interrupt flag
l = clock length counters and sweep units
e = clock envelopes and triangle's linear counter
mode 0: 4-step effective rate (approx)
---------------------------------------
- - - f 60 Hz
- l - l 120 Hz
e e e e 240 Hz
mode 1: 5-step effective rate (approx)
---------------------------------------
- - - - - (interrupt flag never set)
l - l - - 96 Hz
e e e e - 192 Hz
At any time if the interrupt flag is set and the IRQ disable is clear, the
CPU's IRQ line is asserted.
--------------
Length Counter
--------------
A length counter allows automatic duration control. Counting can be halted and
the counter can be disabled by clearing the appropriate bit in the status
register, which immediately sets the counter to 0 and keeps it there.
The halt flag is in the channel's first register. For the square and noise
channels, it is bit 5, and for the triangle, bit 7:
--h- ---- halt (noise and square channels)
h--- ---- halt (triangle channel)
Note that the bit position for the halt flag is also mapped to another flag in
the Length Counter (noise and square) or Linear Counter (triangle).
Unless disabled, a write the channel's fourth register immediately reloads the
counter with the value from a lookup table, based on the index formed by the
upper 5 bits:
iiii i--- length index
bits bit 3
7-4 0 1
-------
0 $0A $FE
1 $14 $02
2 $28 $04
3 $50 $06
4 $A0 $08
5 $3C $0A
6 $0E $0C
7 $1A $0E
8 $0C $10
9 $18 $12
A $30 $14
B $60 $16
C $C0 $18
D $48 $1A
E $10 $1C
F $20 $1E
See the clarifications section for a possible explanation for the values left
column of the table.
When clocked by the frame sequencer, if the halt flag is clear and the counter
is non-zero, it is decremented.
---------------
Status Register
---------------
The status register at $4015 allows control and query of the channels' length
counters, and query of the DMC and frame interrupts. It is the only register
which can also be read.
When $4015 is read, the status of the channels' length counters and bytes
remaining in the current DMC sample, and interrupt flags are returned.
Afterwards the Frame Sequencer's frame interrupt flag is cleared.
if-d nt21
IRQ from DMC
frame interrupt
DMC sample bytes remaining > 0
triangle length counter > 0
square 2 length counter > 0
square 1 length counter > 0
When $4015 is written to, the channels' length counter enable flags are set,
the DMC is possibly started or stopped, and the DMC's IRQ occurred flag is
cleared.
---d nt21 DMC, noise, triangle, square 2, square 1
If d is set and the DMC's DMA reader has no more sample bytes to fetch, the DMC
sample is restarted. If d is clear then the DMA reader's sample bytes remaining
is set to 0.
------------------
Envelope Generator
------------------
An envelope generator can generate a constant volume or a saw envelope with
optional looping. It contains a divider and a counter.
A channel's first register controls the envelope:
--ld nnnn loop, disable, n
Note that the bit position for the loop flag is also mapped to a flag in the
Length Counter.
The divider's period is set to n + 1.
When clocked by the frame sequencer, one of two actions occurs: if there was a
write to the fourth channel register since the last clock, the counter is set
to 15 and the divider is reset, otherwise the divider is clocked.
When the divider outputs a clock, one of two actions occurs: if loop is set and
counter is zero, it is set to 15, otherwise if counter is non-zero, it is
decremented.
When disable is set, the channel's volume is n, otherwise it is the value in
the counter. Unless overridden by some other condition, the channel's DAC
receives the channel's volume value.
-----
Timer
-----
All channels use a timer which is a divider driven by the ~1.79 MHz clock.
The noise channel and DMC use lookup tables to set the timer's period. For the
square and triangle channels, the third and fourth registers form an 11-bit
value and the divider's period is set to this value *plus one*.
llll llll low 8 bits of period (third register)
---- -hhh upper 3 bits of period (fourth register)
----------
Sweep Unit
----------
The sweep unit can adjust a square channel's period periodically. It contains a
divider and a shifter.
A channel's second register configures the sweep unit:
eppp nsss enable, period, negate, shift
The divider's period is set to p + 1.
The shifter continuously calculates a result based on the channel's period. The
channel's period (from the third and fourth registers) is first shifted right
by s bits. If negate is set, the shifted value's bits are inverted, and on the
second square channel, the inverted value is incremented by 1. The resulting
value is added with the channel's current period, yielding the final result.
When the sweep unit is clocked, the divider is *first* clocked and then if
there was a write to the sweep register since the last sweep clock, the divider
is reset.
When the channel's period is less than 8 or the result of the shifter is
greater than $7FF, the channel's DAC receives 0 and the sweep unit doesn't
change the channel's period. Otherwise, if the sweep unit is enabled and the
shift count is greater than 0, when the divider outputs a clock, the channel's
period in the third and fourth registers are updated with the result of the
shifter.
--------------
Square Channel
--------------
+---------+ +---------+
| Sweep |--->|Timer / 2|
+---------+ +---------+
| |
| v
| +---------+ +---------+
| |Sequencer| | Length |
| +---------+ +---------+
| | |
v v v
+---------+ |\ |\ |\ +---------+
|Envelope |------->| >----------->| >----------->| >-------->| DAC |
+---------+ |/ |/ |/ +---------+
There are two square channels beginning at registers $4000 and $4004. Each
contains the following: Envelope Generator, Sweep Unit, Timer with
divide-by-two on the output, 8-step sequencer, Length Counter.
$4000/$4004: duty, envelope
$4001/$4005: sweep unit
$4002/$4006: period low
$4003/$4007: reload length counter, period high
In addition to the envelope, the first register controls the duty cycle of the
square wave, without resetting the position of the sequencer:
dd-- ---- duty cycle select
d waveform sequence
---------------------
_ 1
0 - ------ 0 (12.5%)
__ 1
1 - ----- 0 (25%)
____ 1
2 - --- 0 (50%)
_ _____ 1
3 -- 0 (25% negated)
When the fourth register is written to, the sequencer is restarted.
The sequencer is clocked by the divided timer output.
When the sequencer output is low, the DAC receives 0.
--------------
Linear Counter
--------------
The Linear Counter serves as a second more-accurate duration counter for the
triangle channel. It contains a counter and an internal halt flag.
Register $4008 contains a control flag and reload value:
crrr rrrr control flag, reload value
Note that the bit position for the control flag is also mapped to a flag in the
Length Counter.
When register $400B is written to, the halt flag is set.
When clocked by the frame sequencer, the following actions occur in order:
1) If halt flag is set, set counter to reload value, otherwise if counter
is non-zero, decrement it.
2) If control flag is clear, clear halt flag.
----------------
Triangle Channel
----------------
+---------+ +---------+
|LinearCtr| | Length |
+---------+ +---------+
| |
v v
+---------+ |\ |\ +---------+ +---------+
| Timer |------->| >----------->| >------->|Sequencer|--->| DAC |
+---------+ |/ |/ +---------+ +---------+
The triangle channel contains the following: Timer, 32-step sequencer, Length
Counter, Linear Counter, 4-bit DAC.
$4008: length counter disable, linear counter
$400A: period low
$400B: length counter reload, period high
When the timer generates a clock and the Length Counter and Linear Counter both
have a non-zero count, the sequencer is clocked.
The sequencer feeds the following repeating 32-step sequence to the DAC:
F E D C B A 9 8 7 6 5 4 3 2 1 0 0 1 2 3 4 5 6 7 8 9 A B C D E F
At the lowest two periods ($400B = 0 and $400A = 0 or 1), the resulting
frequency is so high that the DAC effectively outputs a value half way between
7 and 8.
-------------
Noise Channel
-------------
+---------+ +---------+ +---------+
| Timer |--->| Random | | Length |
+---------+ +---------+ +---------+
| |
v v
+---------+ |\ |\ +---------+
|Envelope |------->| >----------->| >------->| DAC |
+---------+ |/ |/ +---------+
The noise channel starts at register $400C and contains the following: Length
Counter, Envelope Generator, Timer, 15-bit right shift register with feedback,
4-bit DAC.
$400C: envelope
$400E: mode, period
$400F: reload length counter
Register $400E sets the random generator mode and timer period based on a 4-bit
index into a period table:
m--- iiii mode, period index
i timer period
----------------
0 $004
1 $008
2 $010
3 $020
4 $040
5 $060
6 $080
7 $0A0
8 $0CA
9 $0FE
A $17C
B $1FC
C $2FA
D $3F8
E $7F2
F $FE4
The shift register is clocked by the timer and the vacated bit 14 is filled
with the exclusive-OR of *pre-shifted* bits 0 and 1 (mode = 0) or bits 0 and 6
(mode = 1), resulting in 32767-bit and 93-bit sequences, respectively.
When bit 0 of the shift register is set, the DAC receives 0.
On power-up, the shift register is loaded with the value 1.
------------------------------
Delta Modulation Channel (DMC)
------------------------------
+----------+ +---------+
|DMA Reader| | Timer |
+----------+ +---------+
| |
| v
+----------+ +---------+ +---------+ +---------+
| Buffer |----| Output |---->| Counter |---->| DAC |
+----------+ +---------+ +---------+ +---------+
The DMC can output samples composed of 1-bit deltas and its DAC can be directly
changed. It contains the following: DMA reader, interrupt flag, sample buffer,
Timer, output unit, 7-bit counter tied to 7-bit DAC.
$4010: mode, frequency
$4011: DAC
$4012: address
$4013: length
On power-up, the DAC counter contains 0.
Register $4010 sets the interrupt enable, loop, and timer period. If the new
interrupt enabled status is clear, the interrupt flag is cleared.
il-- ffff interrupt enabled, loop, frequency index
f period
----------
0 $1AC
1 $17C
2 $154
3 $140
4 $11E
5 $0FE
6 $0E2
7 $0D6
8 $0BE
9 $0A0
A $08E
B $080
C $06A
D $054
E $048
F $036
A write to $4011 sets the counter and DAC to a new value:
-ddd dddd new DAC value
Sample Buffer
-------------
The sample buffer either holds a single sample byte or is empty. It is filled
by the DMA reader and can only be emptied by the output unit, so once loaded
with a sample it will be eventually output.
DMA Reader
----------
The DMA reader fills the sample buffer with successive bytes from the current
sample, whenever it becomes empty. It has an address counter and a bytes remain
counter.
When the DMC sample is restarted, the address counter is set to register $4012
* $40 + $C000 and the bytes counter is set to register $4013 * $10 + 1.
When the sample buffer is in an empty state and the bytes counter is non-zero,
the following occur: The sample buffer is filled with the next sample byte read
from memory at the current address, subject to whatever mapping hardware is
present (the same as CPU memory accesses). The address is incremented; if it
exceeds $FFFF, it is wrapped around to $8000. The bytes counter is decremented;
if it becomes zero and the loop flag is set, the sample is restarted (see
above), otherwise if the bytes counter becomes zero and the interrupt enabled
flag is set, the interrupt flag is set.
When the DMA reader accesses a byte of memory, the CPU is suspended for 4 clock
cycles.
Output Unit
-----------
The output unit continually outputs complete sample bytes or silences of equal
duration. It contains an 8-bit right shift register, a counter, and a silence
flag.
When an output cycle is started, the counter is loaded with 8 and if the sample
buffer is empty, the silence flag is set, otherwise the silence flag is cleared
and the sample buffer is emptied into the shift register.
On the arrival of a clock from the timer, the following actions occur in order:
1. If the silence flag is clear, bit 0 of the shift register is applied to
the DAC counter: If bit 0 is clear and the counter is greater than 1, the
counter is decremented by 2, otherwise if bit 0 is set and the counter is less
than 126, the counter is incremented by 2.
1) The shift register is clocked.
2) The counter is decremented. If it becomes zero, a new cycle is started.
----------
DAC Output
----------
The DACs for each channel are implemented in a way that causes non-linearity
and interaction between channels, so calculation of the resulting amplitude is
somewhat involved.
The normalized audio output level is the sum of two groups of channels:
output = square_out + tnd_out
95.88
square_out = -----------------------
8128
----------------- + 100
square1 + square2
159.79
tnd_out = ------------------------------
1
------------------------ + 100
triangle noise dmc
-------- + ----- + -----
8227 12241 22638
where triangle, noise, dmc, square1 and square2 are the values fed to their
DACs. The dmc ranges from 0 to 127 and the others range from 0 to 15. When the
sub-denominator of a group is zero, its output is 0. The output ranges from 0.0
to 1.0.
Implementation Using Lookup Table
---------------------------------
The formulas can be efficiently implemented using two lookup tables: a 31-entry
table for the two square channels and a 203-entry table for the remaining
channels (due to the approximation of tnd_out, the numerators are adjusted
slightly to preserve the normalized output range).
square_table [n] = 95.52 / (8128.0 / n + 100)
square_out = square_table [square1 + square2]
The latter table is approximated (within 4%) by using a base unit close to the
DMC's DAC.
tnd_table [n] = 163.67 / (24329.0 / n + 100)
tnd_out = tnd_table [3 * triangle + 2 * noise + dmc]
Linear Approximation
--------------------
A linear approximation can also be used, which results in slightly louder DMC
samples, but otherwise fairly accurate operation since the wave channels use a
small portion of the transfer curve. The overall volume will be reduced due to
the headroom required by the DMC approximation.
square_out = 0.00752 * (square1 + square2)
tnd_out = 0.00851 * triangle + 0.00494 * noise + 0.00335 * dmc
This linear approximation neglects the attenuating effect the DMC has when its
DAC is in the upper level. This factor can be calculated using the main formula
to form a ratio, and precalculated into a 128-entry lookup table.
tnd_out(triangle=15,dmc=d) - tnd_out(triangle=0,dmc=d)
attenuation(d) = ------------------------------------------------------
tnd_out(triangle=15,dmc=0)
-------------------
Unreliable Behavior
-------------------
(The following behaviors probably don't need to be emulated due to their
unreliability since stable code will avoid invoking it, and since their
behavior is somewhat difficult to precisely predict.)
If the frame IRQ is set just as register $4015 is being read, it seems to be
ignored (similar to polling $2002 for the vbl flag).
The DMC's DMA reader seems to check for an empty buffer every few CPU cycles,
rather than every cycle or continuously.
Writing to the DAC register ($4011) while a sample is playing sometimes has no
effect, probably because the DMC's output unit is clocking the counter at the
same moment as the write.
--------------
Clarifications
--------------
(The following are meant only as re-statements of the main content, rather than
additions of new content.)
Because the envelope loop and length counter disable flags are mapped to the
same bit, the length counter can't be used while the envelope is in loop mode.
Similar applies to the triangle channel, where the linear counter and length
counter are both controlled by the same bit in register $4008.
Unlike the other waveform channels, the triangle channel is silenced by
stopping its waveform at whatever phase it's at, rather than causing zero to be
sent to its DAC.
The length counter table seems to be set up for standard note durations for 4/4
time at 160 bpm and 180 bpm. If bit 3 is 0, the following results (Dn is bit n
of the fourth channel register):
180bpm 160bpm
D6-D4 D7=0 D7=1 note
-------------------------------
$00 10 12 16th
$01 20 24 8th
$02 40 48 4th (one beat)
$03 80 96 half
$04 160 192 whole
$05 60 72 4th dotted
$06 14 16 8th triplet (*3 = a 4th)
$07 26 32 4th triplet (*3 = a half)
-------------
Collaborators
-------------
Brad Taylor's NESSOUND.TXT and DMC.TXT as a starting point for testing.
NTSC NES for testing on.
Nesdev forum for feedback.
xodnizel for testing results, correction to DMC table, feedback.
Bloopaws/Draci for feedback, possible explanation of length counter table
values.
-------
History
-------
2003.12.01
Made development cartridge and started testing on NES hardware.
2003.12.14
Started project.
2003.12.20
A few draft sections were posted to Nesdev or e-mailed privately.
2004.01.02
Draft version posted to Nesdev. Corrected tnd_table formula.
2004.01.02
Corrected incorrect "correction" to tnd_table formula. Double-checked them.
2004.01.03
Corrected envelope flag name to "disable" (it was named "enable").
Added effective frequencies of frame sequencer outputs.
Added Overview, Unreliable Behavior, Clarifications, and Collaborators
sections.
2004.01.04
Adjusted linear approximation (difficult to find a compromise).
A few minor edits.
2004.01.30
First release. Probably won't be doing much with it for a while.
TEK E7 electronique analogique, studio & sound system
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