Oneshot Pulse Output; Time Interval Measurements - Keithley DAS-8 Series User Manual

Logical Counters 3 and 4 can generate square and variable duty cycle
waves using the internal clock. However, arbitrary duty cycles are not
possible. The onCount must be 3 off count (=period - onCount) and the
onCount
ratio
----------------------
off count
If the above conditions are not met, the onCount will be adjusted to
comply.
Output pulses cannot be entirely stopped, only slowed to a period of
1.2(0.12)(hr).

Oneshot Pulse Output

A single TTL pulse can be output by setting the pulses field in the Rate
Event to 1. However, hardware restrictions of the DAS-8 timers do not
allow exact compliance with the DriverLINX API. The pulse output is
inverted (active low); the Intel 8254 cannot generate a single active high
pulse. A warning message about inverted pulse levels is always returned
by DriverLINX when using the DAS-8.
To implement oneshot pulse outputs, DriverLINX uses Mode 0 of the
Intel 8254 (pulse on terminal count): Output goes low when counter is
loaded and remains low until end of count. The gate must be high for
counting. Actual delay is onCount + mode setup time (as loading control
register forces output low).
Note: Only the onCount determines duration; the period count is ignored.

Time Interval Measurements

DriverLINX does not support Time Interval Measurements using the
DAS-8.
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must be an integer.
C-15