Bay Technical Associates V79 PDI-1 - Manual (Page 20)

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The PDI module can observe, record, and report when an event happened, how
long the event lasted, and how many events occurred for each individual channel.
The initial occurrence of an event will set the event latch bit and store the
associated time in the latch buffer. You may read the state of the initial event and
the time it was recorded (if time tagging is enabled) by issuing the RL or RR
commands.
Each occurrence of an event starts the duration counter and increments the event
counter. The duration counter measures event duration time in milliseconds with a
maximum time of 65,535 stored. You may read the duration of the last recorded
event by issuing the RD command.
NOTE: Duration measurements are not de-bounced. If the input circuit cycles
between active and inactive before settling, only the settled value is reported.
Therefore, if a PDI module is connected to a relay or switch that has "dirty"
contacts, the total measurement will be less than the actual activation duration of
the circuit by the amount of time spent settling.
The event counter reflects the total number of events that have occurred since the
event counter was last cleared using the CC or RO command. You may read the
current event counter value by sending the RC or RO command. The event
counter will trigger on the rising edge of an event when LO to HI Latch Polarity is
selected or on the falling edge of an event when HI to LO Latch Polarity is
selected. Examples of using the event counter would include counting items
moving on a conveyor belt and process control where a pre-determined number of
events must take place before a defined action may take place.
NOTE: An event must have a duration greater than one millisecond plus the
current debounce delay time to increment the event counter.