WANUGA%MIT-XX@sri-unix.UUCP (11/02/83)
From: Thomas S. Wanuga <WANUGA@MIT-XX>
I have been looking into changing the driver for the IBMPC keyboard
under DOS 2.00. Specifically I am interested in changing the size of
the type-ahead buffer and turning off the auto-repeat feature. I have
looked at the keyboard section in the Technical Reference manual,
including the ROM code for the keyboard driver. There are a few
things that I can't figure out, and I was wondering if some kind soul
could explain them to me.
1) How or why do autorepeat keys work?
2) How does the driver note the state of the shift key? In
particular, how does it distinguish between holding down SHIFT and
another key at the same time, and pressing and realeasing the
SHIFT key and then hitting another key?
3) What causes the keyboard (not the keyboard driver) to send an
overrun code (scan code = 0FFh)? Is it sent whenever the keyboard
buffer (not the type-ahead buffer) overflows? If so, does it send
just one overrun code after the 20 scan codes, even if it
overflowed by more thatn one key?
Thanks.
Tom Wanuga
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