National Instruments AT-DIO-32F, User Manual

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Chapter 4 Programming
© National Instruments Corporation 4-33 AT-DIO-32F User Manual
CNTRCMD Register
The CNTRCMD Register contains eight bits that determine the counter selection, counter size,
counting format, and operation mode.
Address: Base a 1E (hex)
Type: Write-only
Word Size: 8-bit
Bit Map:
7 6 5 4 3 2 1 0
CNTRSEL1 CNTRSEL0 RWSEL1 RWSEL0 MODESEL2 MODESEL1 MODESEL0 BCDSEL
Bit Name Description
7-6 CNTRSEL<1..0> Counter Select Bits.
These bits select the counter on which the command operates.
CNTRSEL1 CNTRSEL0 Operation
0 0 Select Counter 1
0 1 Select Counter 2
1 0 Select Counter 3
1 1 Read-Back command
5-4 RWSEL<1..0> Read/Write Select Bits.
These bits select data written to or read from a counter, or these
bits send a Counter Latch command.
RWSEL1 RWSEL0 Operation
0 0 Counter Latch command
0 1 Read and write least
significant byte only
1 0 Read and write most
significant byte only
1 1 Read and write least
significant byte then
most significant byte