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 Message was sent through the cbm-hackers mailing list
Archive generated by hypermail 2.1.1.