> > I know the I/O port No.00-0F is DMA controller and the port No.20-21 is
> > interrupt controller. But I don't know how to use the port No22 and 23.
> > Anyone know the I/O port No.22,23 meaning on the HP200LX?
>
> Assuming it's simply an 8259, you can find the relevant information in the
> package called HelpPC (in the hardware section), available from:
>
> Under Linux, the PIC is shown as using ports 0x20-0x3f, so it's definitly
> part of the PIC.
Actually it's not. Ports 0x22 and 0x23 are used on many chipsets (mostly
non-intel chipsets, cyrix/AMD processors settings and stuff like that)
and do not belong to PIC.
In this particular case it is Hornet chipset made by HP and is supposed
to be used in LX100/LX200. It can be used to set LCD contrast, clock
speed, et cetera, interesting thing actually. Port 0x22 seems to be
index register and 0x23 chip set data.
You might want to consult Ralph Brown's interrupt list for further
details.
bye, Ab
