Sound MIC output

[ZXcuriosus]

Good morning all,
I'm looking to generate sounds with the MIC port of the ZX81 but I can't find any information on the subject ...
I read that it was port 255 which was used for the MIC output. So I tried in assembler with the OUT instruction of the Z80 to pass the port 255 to 255 (since I do not know the exact bit which is used) then then to zero with a deceleration loop so as to generate a signal d 'about 3khz but I got no signal on the MIC output ...
If someone has already tried to manipulate the MIC output I would be interested to have some information

Thanks in advance to all

[Paul]

Welcome to our forums.
Have a look at mastering machine code on your zx81 chapter 12

http://www.users.waitrose.com/~thunor/m ... ter12.html

Kind regards Paul

[ZXcuriosus]

Good-morning Paul,

Thanks a lot for your help !
I was able to download the little program from chapter 12 which works very well and generates nice notes on the MIC output of the ZX81
I will now be able to study the program closely and then do my own assembly routines.

Again thanks to you

[Paul]

You are welcome.

[1024MAK]

You may also find this link useful. The key point is that you have to use IN as well as OUT.

Mark