Posted By
Csabo
on 2016-05-17
13:36:27
|  Re: How to detect SID card?
Sorry, I don't remember the source, but I have this code. You can detect it at any of the 2 usual base addresses ($FD40, $FE80).
1) Write $41 to base address + $12.
2) Write $55 to base address + $1B and wait a few cycles.
Write a loop for 256 times that checks:
3) Check base address + $1B AND #$FE.
4) If it's $00, keep looping. When the loop ends, there IS a SID card.
5) If it's NOT $FE, there's no SID card, you can exit the loop.
Hopefully it makes sense  There might be simpler ways, but AFAIK this works reliably and it's pretty short/fast.
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