stu@jpusa1.UUCP (03/20/87)
I would like to add drivers for additional ports as com3,4 using ints
11,12 and am stumped concerning the interrupt code. I have the driver
working as a polled driver (this is standard 8250 stuff, just like a
plain vanilla asynch com1,2 port) but the documentation does not go into
any detail on dealing with the system interrupt controller. I assume it
needs to be initialized and also need to know if it needs to be
re-initialized on receipt of an interrupt. Ditto for the 8250. The ibm
technical reference says concerning the 8250 Interrupt Identification
Register:
The interrupt identification register (IIR), when addressed during
chip-select time, freezes the highest priority interrupt pending,
and no other interrupts are acknowledged until that particular
interrupt is serviced by the processor.
What constitutes 'serviced by the processor'? Do you have to reenable
or reinitialize something? The supplied driver does the necessary
initialization and I get exactly one interrupt with my code. If I take
the supplied serial driver out of the link altogether, I can't get any
interrupts at all. I'm stumped. I'm aware that a typical dos driver
will do a 'non specific end of interrupt' in the interrupt handler and
don't know whether that's done by the kernal or also needs to be in my
driver code. I do have initialization code for the 8250 Interrupt
Enable Register, so I don't think that's the problem. If anyone knows
how this works, please e-mail me with an explanation.
Thanks in advance.
Stu Heiss {gargoyle,ihnp4}!jpusa1!stu
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Stu Heiss {gargoyle,ihnp4}!jpusa1!stu