@nataliapc/mcp-openmsx

# SOUND ## Effect Writes a value in a specific PSG register. Sound registers 14 and 15 and the two highest bits of register 7 are not accessible with this instruction. ## Syntax `SOUND <PSGregister>,<Value>` ## Parameters `<PSGregister>` is the register number (0-13) to write. It can be a variable or an expression. `<Value>` is a value whose limits depend on the register to write (see Registers Description below). It can be a variable or an expression. _Recommendation for maximum compatibility: when you write register 7 it is good habit to set bit 7 and reset bit 6 although these potentially harmful values should not end up to PSG in any case. That's why only the values 128 to 191 are mentioned below for this register._ ## Registers Description |Register|Description|Values| |---|---|---| |0|Least significant bits of channel A frequency|0~255| |1|Most significant bits of channel A frequency|0~15| |2|Least significant bits of channel B frequency|0~255| |3|Most significant bits of channel B frequency|0~15| |4|Least significant bits of channel C frequency|0~255| |5|Most significant bits of channel C frequency|0~15| |6|Noise generator frequency|0~31| |7|Mixer setting|128~191| |8|Volume of channel A|0~16| |9|Volume of channel B|0~16| |10|Volume of channel C|0~16| |11|Least significant bits of envelope period|0~255| |12|Most significant bits of envelope period|0~255| |13|Envelope shape|0~15| ### About registers 0 to 5 - The value indicating the frequency to be produced on a channel is 12 bits. It is therefore divided into two registers. The value to be written is obtained using the following expression: `Value = Fi / (16 x Fn)` `Fi` = Internal frequency of PSG (1789772.5 Hz on MSX). `Fn` = Frequency of the sound to be produced (varies between 27 and 111.860 Hz). Additional math: `Note + Octave = Note/2` `Note + HalfNote = Note/2^(1/12)` For simplicity, here is ready table of musical notes by octave obtained according to the value indicated in the registers 0~1, 2~3 or 4~5: |Note|O1|O2|O3|O4|O5|O6|O7|O8| |---|---|---|---|---|---|---|---|---| |C|D5Dh|6AFh|357h|1ACh|0D6h|06Bh|035h|01Bh| |C#|C9Ch|64Eh|327h|194h|0CAh|065h|032h|019h| |D|BE7h|5F4h|2FAh|17Dh|0BEh|05Fh|030h|018h| |D#|B3Ch|59Eh|2CFh|168h|0B4h|05Ah|02Dh|016h| |E|A9Bh|54Eh|2A7h|153h|0AAh|055h|02Ah|015h| |F|A02h|501h|281h|140h|0A0h|050h|028h|014h| |F#|973h|4BAh|25Dh|12Eh|097h|04Ch|026h|013h| |G|8EBh|476h|23Bh|11Dh|08Fh|047h|024h|012h| |G#|86Bh|436h|21Bh|10Dh|087h|043h|022h|011h| |A|7F2h|3F9h|1FDh|0FEh*|07Fh|040h|020h|010h| |A#|780h|3C0h|1E0h|0F0h|078h|03Ch|01Eh|00Fh| |B|714h|38Ah|1C5h|0E3h|071h|039h|01Ch|00Eh| (*) 0FEh is the note produced by a tuning fork. ### About register 6 The value indicating the frequency of the white noise generator is 5 bits. The value to be written is obtained using the following formula: `Value = Fi / (16 x Fb)` `Fi` = Internal frequency of PSG (1789772.5 Hz on MSX). `Fb` = Noise frequency master to be produced (varies between 3.608 and 111.860 Hz). ### About register 7 This register is used to activate or deactivate the tone generator as well as the noise generator. The format of the value is as follows: |PSG I/O ports Bit7 - Bit6|Disabling noise Bit5 - Bit4 - Bit3|Disabling tone Bit2 - Bit1 - Bit 0| |:-:|:-:|:-:| |B=1 - A=0|channelC - channelB - channelA |channelC - channelB - channelA| Bits 7 and 6 serves to specify the direction of PSG I/O ports. Always set bit 7 and reset bit 6. Otherwise some devices connected to the joystick ports may malfunction. ### About register 8 to 10 The format of these registers is as follows: |Bit 7|Bit 6|Bit 5|Bit 4|Bit 3 - Bit 2 - Bit 1 - Bit 0| |:-:|:-:|:-:|:-:|:-:| |-|-|-|V/A|Volume / Amplitude of the channel| Reset bit 4 (V/A) to adjust the volume of the corresponding channel, if set the volume will vary in proportion to the envelope shape defined by register 13. ### About register 11 to 13 The registers 11 and 12 control the envelope period. The value is on 16 bits (0~65535). It is calculated with the following expression: `Value = Fi / (256 x T)` `Fi` = Internal frequency of PSG (1789772.5 Hz on MSX). `T` = Period of the envelope (in μs) The register 13 defines the envelope shape. Here are the possible shapes: - 0~3 ＼＿＿＿＿＿＿＿ - 4~7 ／＿＿＿＿＿＿＿ - 8 ＼＼＼＼＼＼＼＼ - 9 ＼＿＿＿＿＿＿＿ - 10 ＼／＼／＼／＼／ - 11 ＼￣￣￣￣￣￣￣ - 12 ／／／／／／／／ - 13 ／￣￣￣￣￣￣￣ - 14 ／＼／＼／＼／＼ - 15 ／＿＿＿＿＿＿＿ ## Examples ```basic 5 ' Initializes the sound registers of the PSG 10 FOR R=0 TO 13 20 IF R=7 THEN SOUND R,&B10111111 ELSE SOUND R,0 30 NEXT 40 ' Plays the note C on channel A with a volume of 12 50 SOUND 0,&hAC ' 8 least significant bits of frequency on channel A 60 SOUND 1,1 ' 4 most significant bits of frequency on channel A 70 SOUND 8,&b1100 ' Sets the volume to 12 on channel A 80 SOUND 7,&b10111110 ' Activates the sound generator on channel A ``` Same example in decimal mode for the values: ```basic 5 ' Initializes the sound registers of the PSG 10 FOR R=0 TO 13 20 IF R=7 THEN SOUND R,191 ELSE SOUND R,0 30 NEXT 40 ' Plays the note C on channel A with a volume of 12 50 SOUND 0,172 ' 8 least significant bits of frequency on channel A 60 SOUND 1,1 ' 4 most significant bits of frequency on channel A 70 SOUND 8,12 ' Sets the volume to 12 on channel A 80 SOUND 7,190 ' Activates the sound generator on channel A ``` Legendary Finnish sauna-effect (_Source: MikroBitti 12/1987_): ```basic 10 REM SAUNONTA-TEHOSTE 20 SOUND 7,&B10110111 30 SOUND 8,16 40 SOUND 6,2 50 SOUND 12,160 60 SOUND 13,0 70 FOR T=1 TO 3500:NEXT 80 KO=INT(RND(1)*7)+2 90 SOUND 6,KO 100 M=INT(RND(1)*2)+3 110 SOUND 12,M 120 SOUND 13,4 130 AV=INT(RND(1)*50)+250 140 FOR T=1 TO AV:NEXT 150 N=N+1:IF N<LL THEN 80 160 N=0:LL=INT(RND(1)*15)+10 170 FOR T=1 TO 1000:NEXT 180 GOTO 40 ``` ## Related to `BEEP`, `PLAY`, `PLAY()` ## Compatibility MSX-BASIC 1.0 or higher ## Links - [General Instrument AY-3-8910 application manual](http://map.grauw.nl/resources/sound/generalinstrument_ay-3-8910.pdf) - [Yamaha YM2149 SSG application manual](http://map.grauw.nl/resources/sound/yamaha_ym2149.pdf) ## Source Retrieved from "https://www.msx.org/wiki/SOUND"