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Lex Van AY-3-8910 PSG

AY-3-8910 sound generator and joy stick port design by Lex Van Sonderen first published in ACE User 4 1983.



The AY-3-8910 is a 3-voice programmable sound generator (PSG) designed by General Instrument, initially for use with their 16-bit CP1610 and other 8-bit microcomputers. The chip also has two general-purpose 8-bit parallel I/O ports, A and B. Its the same chip that's used in the sound card made by Essex Micro Electronic and also in AMI (more AY-3-8910 details can be found here on the AMI page).

Components are:                       Qty

A Y-3-8910 PSG                         1
79 LS 02                               1
79 LS 32                               1
LM 386                                 1
I/O SOCKET to fit ATARI-type joystick  1
3.5 mm SOCKET (Base and switch)        1
L S. 8 Ohm                             1
Resistor 2.7 Ohm                       1
         470 Ohm                       2
         1 k Ohm                       11
Variable resistor  1k Ohm              1
Capacitor 47uF                         1
          100uf                        2
          0.1uf                        5
          330pF                        1
23-Way Edge Connector                  1


In Holland this cost me about £18 I think it will cost about £12-15 in the UK (1984 prices).


The programmable sound generator contains 16 registers, and is addressed with the commands


221 OUT
223 OUT
221 IN


Entering N 221 OUT (N=0 to 15) selects the current register, and N 223 OUT puts value N in registers last pointed to by N 221 OUT. 


I use : REG 221 OUT ;
      : SET 223 OUT ;
      : REG? REG 221 IN ;


EG. 6 REG points to register 6, and
25 SET puts 25 into register 6.
6 REG? returns the current value of register 6


Register # Use Values
1 & 0 Low and High bytes of channel A pitch. 0-255
0-31
2 & 3 Low and High bytes of channel B pitch. 0-255
0-31
4 & 5 Low and High bytes of channel C pitch. 0-255
0-31
3 Noise period on all channels 0-31
7 On-Off selection (see below) (see below)
8 Volume of channel A 0-15
9 Volume of channel B 0-15
10 Volume of channel C 0-15
11 & 12 Low and High bytes of Envelope Duration 0-255
0-255
13 Envelope Shape (see below) (see below)
14 I/O port A data register  
15 I/O port B data register  

Register 7 details:
Decimal 128 64 32 16 8 4 2 1
Bit 7 6 5 4 3 2 1 0
Use B
I/O		 A
I/O		 C
Noise		 B
Noise		 A
Noise		 A
Tone		 B
Tone		 C
Tone
When BITs 0-5 are set (1) the channel is OFF , When BITs 0-5 are reset (0) the channel is ON
so any combination of tone and noise channels is possible.
When BITs 6 & 7 are SET (1) the ports are OUTPUT, When reset (0) the ports are INPUT
Register 8-10 details:
Decimal 128 64 32 16 8 4 2 1
Bit 7 6 5 4 3 2 1 0
Use X X X E V V V V
X - Not Used, E - Envelope enable (set (1) on, reset (0) off, V - General volume control 0-15

Register 13 Envelope shape
Dec Bit 3 Bit 2 Bit 1 Bit 0 Shape
0-3 0 0 x x
4-7 0 1 x x
8 1 0 0 0
9 1 0 0 1
10 1 0 1 0
11 1 0 1 1
12 1 1 0 0
13 1 1 0 1
14 1 1 1 0
15 1 1 1 1
Envelope control is switched on by setting bit 4 of the volume register of the required channel, see Register 8-10 details above.


I wish you a lot of success building it. When you think it works, enter the following:

: REG 221 OUT ;
: SET 223 OUT ;
: REG? 221 OUT 221 IN ;

Try the following:

0 REG 200 SET
7 REG 254 SET
8 REG 8 SET IN

It should produce a continuous tone if it fails, enter:

0 REG?
7 REG?
8 REG?

It should print 200 It should print 254
It should print 8

If not, your PSG is not properly connected. When it is, and if it still fault , the amplifier part or the clock part is not, properly connected. To put all sound off:


Some Examples:

6 REG 8 SET 7 REG 247 SET 8 REG 16 SET 12 REG 20 SET 13 REG I SET ( Shot. )


0 REG 16 SET 7 REG 247 SET 8 REG 16 SET 12 REG 10 SET 13 REG 4 SET (Snap as in Pacman)


7 REG 255 SET 6 REG 28 SET 7 REG 247 SET 8 REG 16 SET 12 REG 20 SET 13 REG 1 SET ( Explode)


6 REG 20 SET 7 REG 247 SET 8 REG 16 SET 12 REG' 50 SET 13 REG 10 SET (Sea Waves)


0 REG 200 SET 7 REG 254 SET 8 REG 16 SET 12 REG 20 SET 13 REG 1 SET (Ping)


0 REG 200 SET 2 REG 201 SET 4 REG 100 SET 7 REG 248 SET 8 REG 16 SET
9 REG 16 SET 10 REG 16 SET 12 REG 20 SET 13 REG 8 SET (Twangy Piano)