Cutler-Hammer D320 PLC, User Manual

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Appendix B: PID Loop Control
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TABLE 1 – PID Block Memory Map
Loop Number Parameter Block Starting Address* Control Bits
0 [SR008] F14.0-F14.3
1 [SR008]+32 F14.4-F14.7
2 [SR008]+64 F14.8-F14.11
3 [SR008]+96 F14.12-F14.15
4 [SR008]+128 F15.0-F15.3
5 [SR008]+160 F15.4-F15.7
6 [SR008]+192 F15.8-F15.11
7 [SR008]+224 F15.12-F15.15
Note: [SR008] indicates the value in SR008. For example, if SR008 holds the value 1000, then Loop
0 starts in W1000, Loop 1 starts in W1032, etc.
Each loop has 4 control bits assigned to it, as shown in the table above. The control bits perform the
following functions:
TABLE 2 – PID Loop Control Bits
Bit Number Description
0 PID Operation/Stop Flag: 1=Operating, 0=Stopped
1 Parameter Setting Error Flag: 1=Range Error, 0=normal
2 CV Value Setting Mode: 1=Manual, 0=PID Loop
3 PID Execution Completion Flag: 1=Complete, 0=Calculating
PID Operation/Stop Flag : This flag defines whether the PID Loop is turned On. When the flag is
On, the PID loop is turned On. When this bit is off, no PID loop calculations are performed.
Parameter Setting Error Flag: The D320 PLC checks the value of each PID loop parameter on a
continuous basis to verify that the value is not too large or too small. When one of the parameters goes
out of range, this error flag is turned On.
CV Value Setting Mode: This bit determines whether the Output Value (CV) of the PID loop
calculation is calculated by the PID loop equation, or set to a given constant value (defined by word 14
of the PID loop block – see below).
PID Execution Completion Flag: The PID loop is executed on a constant time basis. While the PID
loop is calculating, this bit is set Off. When the PID loop has completed its calculation, the bit is
turned On, until the next calculation occurs.