Appendix C
Register-Level Programming
©
National Instruments Corporation
C-5
PC-DIO-24/PnP User Manual
Table C-2 shows the control words for setting or resetting each bit in
port C. Notice that bit 7 of the control word is cleared when
programming the set/reset option for the bits of port C.
Register Description for the Interrupt Control Registers
There are two interrupt control registers on the PC-DIO-24PnP. One of
these registers has individual enable bits for the two interrupt lines from
the 82C55A device. The other register has a master interrupt enable bit.
When writing to these registers, set all reserved bits to zero. The bit
maps and signal definitions are listed as follows.
Table C-2.
Port C Set/Reset Control Words
Bit Number
Bit Set Control
Word
Bit Reset
Control Word
The Bit Set or
Reset in Port C
0
0xxx0001
0xxx0000
xxxxxxxb
1
0xxx0011
0xxx0010
xxxxxxbx
2
0xxx0101
0xxx0100
xxxxxbxx
3
0xxx0111
0xxx0110
xxxxbxxx
4
0xxx1001
0xxx1000
xxxbxxxx
5
0xxx1011
0xxx1010
xxbxxxxx
6
0xxx1101
0xxx1100
xbxxxxxx
7
0xxx1111
0xxx1110
bxxxxxxx
