Measurement Computing PCM-DAS16x/16 - Manual (Page 16)

4.4 A/D PACER CLOCK
Many analog acquisitions can be handled by a simple on-board rate divider created by
combining an XTAL with a programmable counter. For those, the on-board 82C54
programmable rate generator supplies the pacing. Some applications require more
flexible rate control.
The PCM-DAS16x/16 analog conversions may be externally triggered and thereby
synchronized with events external to the PC. Conversions may be held off until some
external event, such as a not-to-exceed condition is met. Conversions may be exter-
nally gated so that samples are taken only when an event of interest is occurring, such
as process over normal limits.
Shown here is the A/D pacer clock schematic and the routing of off board trigger
signals.
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