class ZXLib::AYSound

ZXLib::AYSound.¶ ↑

Macros to help program the AY-3-8910/8912 sound chipsets.

Sources

• www.armory.com/~rstevew/Public/SoundSynth/Novelty/AY3-8910/start.html

• faqwiki.zxnet.co.uk/wiki/AY-3-8912

Registers¶ ↑

The AY-3-8910/8912 contains 16 internal registers as follows:

Register        Function                        Range

 0              Channel A fine pitch            8-bit (0-255)
 1              Channel A coarse pitch          4-bit (0-15)
 2              Channel B fine pitch            8-bit (0-255)
 3              Channel B coarse pitch          4-bit (0-15)
 4              Channel C fine pitch            8-bit (0-255)
 5              Channel C coarse pitch          4-bit (0-15)
 6              Noise pitch                     5-bit (0-31)
 7              Mixer                           8-bit (see below)
 8              Channel A volume                4-bit (0-15, see below)
 9              Channel B volume                4-bit (0-15, see below)
10              Channel C volume                4-bit (0-15, see below)
11              Envelope fine duration          8-bit (0-255)
12              Envelope coarse duration        8-bit (0-255)
13              Envelope shape                  4-bit (0-15)
14              I/O port A                      8-bit (0-255)
15              I/O port B                      8-bit (0-255)

Notes

The AY-3-8912 does not contain register 15.

The volume registers (8, 9 and 10) contain a 4-bit setting but if bit 5 is set then that channel uses the envelope defined by register 13 and ignores its volume setting.

The mixer (register 7) is made up of the following bits (low = enabled):

Bit: 7        6        5        4        3        2        1        0
   _         _
   I/O       I/O   Noise    Noise    Noise     Tone     Tone     Tone
     B        A        C        B        A        C        B        A

The AY-3-8912 ignores bit 7 of this register.

Envelope shapes¶ ↑

The AY-3-8910/8912 contains the following preset envelopes or waveforms (set using control register 13). Note that these affect volume only and not the pitch:

 0      \__________     single decay then off

 4      /|_________     single attack then off

 8      \|\|\|\|\|\     repeated decay

 9      \__________     single decay then off

10      \/\/\/\/\/\     repeated decay-attack
          _________
11      \|              single decay then hold

12      /|/|/|/|/|/     repeated attack
         __________
13      /               single attack then hold

14      /\/\/\/\/\/     repeated attack-decay

15      /|_________     single attack then off