National Instruments AT-DIO-32F User Manual page 82

Chapter 4
Read-Back Command
When bits 7 and 6 (CNTRSEL1 and CNTRSEL0) are 1, the CNTRCMD Register can be used to
execute the Read-Back command. With the Read-Back command, the current totals of multiple
counters can be latched in one command. The Read-Back command also can latch the status of
selected counters. The control word format used for the Read-Back command is as follows:
7
CNTRSEL1 CNTRSEL0
Bit Name
7-6 CNTRSEL<1..0>
5 COUNT*
4 STATUS*
3-1 CNTR<3..1>
0 0
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6 5
COUNT*
Description
Counter Select Bits.
Both bits must be one for the Read-Back command to be used.
Read-Back Count Command.
If COUNT* is cleared, the current count in each of the selected
counters is latched. The next read from the selected counter
returns the latched data.
Read-Back Status Command.
If STATUS* is cleared, the current status in each of the selected
counters is latched. The next read from the selected counter
returns the latched data.
Counter Select Bits for Read-Back Command.
These bits select the counters for the Read-Back command; that is,
if CNTR3 and CNTR1 are set, the Read-Back command latches
data for Counter 3 and Counter 1.
Zero Bit.
This bit must be zero for proper operation of the AT-DIO-32F.
4 3
STATUS* CNTR3
4-35
Programming
2 1
CNTR2 CNTR1
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