Advantech PCI-1710HG Especificaciones descargar pdf (Pagina 153)

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latch commands, one for each counter latched.

The read-back command can also latch status information for selected

counter(s) by setting STA bit = 0. The status must be latched to be

read; the status of a counter is accessed by a read from that counter.

The counter status format appears at the beginning of the chapter.

Counter Latch Operation

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 82C54 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.

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Advantech PCI-1710HG Especificaciones Pagina 153