Ruud Baltissen wrote:
>
> Hallo Chris,
>
> > (as it would be unless you explicitly
> > cleared the ATN condition by reading port A before the CLI)
>
> The reason why I asked you can find at
> http://home.hccnet.nl/g.baltissen/chide1.htm
>
> I first was thinking about disabling the IRQ during the whole proces of
> reading a word/byte from the IDE harddisk but now it seems I better cannot
> do that otherwise I run the risk of missing the ATN.
>
That seems to be a correct assumption (I guess the 6522 designers
assumed that these inputs would be used to signal a 'data is available
on port' condition).
However, the following quote from the 6522 data sheet may save your day:
"IF THE CA2/CB2 CONTROL IN THE PCR IS SELECTED AS "INDEPENDENT"
INTERRUPT INPUT, THEN READING OR WRITING THE OUTPUT REGISTER
ORA/ORB WILL NOT CLEAR THE FLAG BIT. INSTEAD, THE BIT MUST BE
CLEARED BY WRITING INTO THE IFR, AS DESCRIBED PREVIOUSLY."
--
Christer Palm
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