ChibiAkumas ASM Programming Forum

www.chibiakumas.com/z80/platform2.php#LessonP18

It's time to move on! We've looked as graphics, and input, but now we need to complete our game... and what game will be complete with Sound Effects!
To start we'll look at the AY sound chip... the exact same chip exists on the CPC,MSX, speccy and even the Atari ST! (no that's not a z80 system!) ...

Hello Keith,

This question is regarding your Chibisound described at

https://www.chibiakumas.com/z80/platform2.php

for the MSX 1 you describe loading the mixer register,which is register 7,
with the value --NNNTTT.

Don't you need to set bit 7 to 1 and bit 6 to 0 when setting
the mixer register (register 7) in the AY sound chip on an MSX 1?-
otherwise it may damage an MSX computer or make the joystick malfunction.
In other words the wrong register value in the mixer register
can cause a short circuit in an MSX and so damage the
computer.

In other words the binary register value should be 10NNNTTT and not
--NNNTTT.

For an example reference the problem is mentioned here

https://www.msx.org/forum/msx-talk/emul ... in-openmsx

But you don't mention it.

This register mixer problem is specific to MSX as far as I am aware.

I think this is the first example I have seen of 8 bit computer software
that has the possibility of damaging the hardware (usually writing buggy
software does not damage the hardware)

To be honest It's the first time I've heard of that problem.

The thread you linked is dated early 2019, my video was actually made late 2018... I'm guessing the problem is probably documented somewhere else, but I hadn't heard of it before, and as the thread says, it doesn't really show up in openMSX

I've updated the documentation with mention of the MSX'es requirement on this field and source code for this lesson accordingly.
Thanks.