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Co u n t e r La t c h Op e r a t i o n
Users often want to read the value of a counter without disturbing the
count in progress. You do this by latching the count value for the
specific counter then reading the value.
The 8254 supports the counter latch operation in two ways. The first
way is to set bits RW1 and RW0 to 0. This latches the count of the
selected counter in a 16-bit hold register. The second way is to
perform a latch operation under the read-back command. Set bits SC1
and SC0 to 1 and CNT = 0. The second method has the advantage of
operating several counters at the same time. A subsequent read
operation on the selected counter will retrieve the latched value.
Co u n t e r Ap p l i cat i o n s
The 8254 compatible programmable interval timer/counter on your
PCI-1751 interface card is a a very useful device. You can program
timers 1 and 2 to serve as timers, event counters, square wave genera-
tors, or as a watchdog to generate regular interrupts at a fixed interval.
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PCI-1751 User's Manual
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