National Instruments PC-LPM-16/PnP User Manual page 108

Appendix D Register-Level Programming
Programming the MSM82C53 Counter/Timer
PC-LPM-16/PnP User Manual
Counters 0, 1, and 2 of the MSM82C53 counter/timer (except the CLK0
signal of counter 1) are available for general-purpose timing
applications. Counter 0 has a fixed 1 MHz clock input and can be used
as the sample interval counter of A/D conversion. Write and read
operations to the MSM82C53 are 8-bit operations. For general
programming details, refer to Appendix B, MSM82C53 Data Sheet.
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