At 11:34 PM 9/29/97 +0100, you wrote:
>Hi
>
>>
>> Thank you for the information, but I still have one question, how does the
>> microprocessor ack the IRQ? I am looking at a diagram of the ISA bus and I
>> don't see any IRQ ack pin or anything like that.
>>
>> Thanks again,
>> Sean
>>
>        The processor does ACK the Interrupt but this goes to the PIC
>(Programmable Interrupt Controler) of the PC. The IRQ lines on the ISA
>bus connect to the PICs and not directly to the processor. About the
>duraction of the pulse I don't have exact numbers at hand, but I think
>that the 5us that someone refered (as it hapens with the printer port)
>are more than enought.
>best regards
>        Jorge F

BTW, talking about 8259, you can look at my homepage about interfacing 8259
to 68hc11.
Sending ack is from software(IRQ handler).
goodluck.
www.poboxes.com/f
f