Appendix B
Register-Level Programming — Register Map and Description
©
National Instruments Corporation
B-9
PCI-DIO-96/PXI-6508/PCI-6503 User Manual
Register Description for the 82C53 (PCI-DIO-96, PXI-6508 Only)
Figure B-3 shows the control word format used to program the 82C53. Bits 7 and 6 of the
control word select the counter to be programmed. Bits 5 and 4 select the mode by which the
count data is written to and read from the selected counter. Bits 3, 2, and 1 select the mode for
the selected counter. Bit 0 selects whether the counter counts in binary or BCD format. After
writing to the Configuration Register to configure a counter, you can read or write the counter
itself eight bits at a time, as controlled by the access mode.
Figure B-3.
Control Word Format for the 82C53
D7
D6
D5
D4
D3
D2
D1
D0
Counter Select
00 = Counter 0
01 = Counter 1
10 = Counter 2
11 = Illegal
Access Mode
00 = Latch counter value
01 = Access LSB only
10 = Access MSB only
11 = Access LSB, then MSB
BCD
1 = Count in BCD
0 = Count in Binary
Mode Select
000 = Mode 0
001 = Mode 1
010 = Mode 2
011 = Mode 3
100 = Mode 4
101 = Mode 5
110 = Mode 2
111 = Mode 3