Allen-Bradley ProcessLogix 1756-IA16, Reference Manual, Page: 83 / 120

Publication 1757-RM810A-EN-P - May 2002
Functional Blocks 3-43
Outputs The POSPROP block has the following initializable outputs:
•
RAISETIME = Raise pulse duration.
•
LOWERTIME = Lower pulse duration.
•
PULSETIME = Pulse duration.
Output Ranges
and Limits The POSPROP block uses the maximum and minimum pulse parameters to define pulse duration ranges and limits.
•
MAXPULSER and MAXPULSEL define the maximum pulse time in the Raise and Lower directions, respectively. The
POSPROP block will not issue a Raise/Lower pulse with a duration that exceeds these values. If the output and
CYCLETIME are greater than MAXPULSER/MAXPULSEL, the output is clamped to MAXPULSER/MAXPULSEL.
•
MINPULSER and MINPULSEL define the minimum pulse time in the Raise and Lower directions, respectively. The
POSPROP block will not issue a Raise/Lower pulse with a duration that is less than these values. If the output is
less than MINPULSER/MINPULSEL, the output retains its old value.
(Note that the POSPROP block does not use these common regulatory control block range and limit parameters:
CVEUHI, CVEULO, OPHILM, OPLOLM, OPEXHILM, and OPEXLOLM.)
Equation
Options The POSPROP block generates Raise and Lower pulses at a rate specified by the configurable cycle time (CYCLETIME)
parameter. It calculates the pulse duration at the beginning of each cycle depending on whether:
•
The PVP is greater than (SPP – ERRORDBR) and the Raise limit flag (RAISELMFL) is OFF, then issue a Raise pulse.
•
The PVP is less than (SPP + ERRORDBL) and the Lower limit flag (LOWERLMFL) is OFF, then issue a Lower pulse.
The PULSETIME output is set to either the RAISETIME or –LOWERTIME, when either RAISETIME or LOWERTIME is
non-zero.
Control
Initialization The POSPROP block accepts initialization information from its three initializable outputs: RAISETIME, LOWERTIME,
and PULSETIME. If any output requests initialization, the POSPROP block sets its INITMAN parameter to ON. When no
output requests initialization, the POSPROP block sets its INITMAN parameter to OFF. When cycling resumes after
initialization, the Raise and Lower outputs are both set to OFF (or their normal states) and the cycle time is restarted.
Override
Feedback
Processing The POSPROP block does not propagate override feedback data. It ignores any override feedback requests.
Parameters on following page
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