75 replies to this topic

[mikey]

Bryan, on Wed Jan 11, 2012 10:04 PM, said:

I'm just curious to find where it stuffs the timer value that's supposed to simulate one disk rotation.

Hi, Bryan
There ...

1610	 LDA #$D2	   for timeout
1620 F1T1 BIT DRA	   write 1 byte 00 at DRQ
1630	 BPL F1T1
1640	 STY DATREG
1650 F1T2 BIT DRA	   another byte 00
1660	 BPL F1T2
1670	 STY DATREG
1680	 STA T1024I  start timer

$d2*1024 cycles (1024T timer) gives 215040 usecs, that would be about 0,21 sec.
At 288 rpm there's 4,8 rotation per second which gives one rotation time of 0,208 sec
Sounds legit Correct me if I am wrong