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Function Blocks
PI Pulse Input
Revision 11
HC900 Hybrid Control Designer Function Block Reference Guide
263
2/07
PI Pulse Input
Description
The PI label stands for Pulse Input.
Function
This function block reads pulses from a single input channel on a Pulse/Frequency/Quadrature input
module. It measures quantity by scaling the number of pulses to engineering units (EU). It measures rate in
engineering units by dividing number of pulses by time. The preset values, reset, preset action, and hold
flags are sent to the module and the module responds with accumulated pulse counts, preset indicator
(PREI) (when preset value is reached), counter overflow indicator (OVFL), and FAIL. The block converts
the accumulated pulse count to EU
Inputs
HOLD
= A Boolean value when set to ON holds the EU count (OUT) at its current value.
RPRES
= Remote preset value (in EU). When OUT reaches this value (or the local preset value) PREI
turns ON.
^RST
= An OFF to ON transition resets the module’s pulse counter and the block’s OUT to zero. It also
clears the FAIL, PREI and OVFL flags.
Outputs
FAIL
= Failed Input Indication. A Boolean value that turns ON when the Pulse/Frequency/Quadrature
Input module reports a failure. This is cleared by the ^RST input.
PREI
= Preset indicator. OFF [0] when OUT = less than the local or remote preset value, ON when the
count (OUT) reaches the local or remote preset value. The hardware module determines the state of the
PREI output. Note: due to the delay in messaging and the responsive time of the module, there can be a lag
between the PREI output of the function block versus the DO on the module. This lag can be as much as 1
scan cycle. PREI is cleared by the ^RST input. A preset value of 0 effectively turns off the Preset allowing
the counter to count continuously until held or reset.
OVFL
= Overflow flag. This turns ON when the counter on the module is full. This is cleared by the
^RST input.
RATE
= Rate in EU/Time Period. Input pulses are counted over a specified Sample Time and scaled to
EU/Second, EU/Minute or EU/Hour.
OUT
= The accumulated Engineering Unit (EU) count. The forcing of OUT is permitted within this block.
Содержание HC900
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