Chapter 7. PID Built-In Function Block
GFK-2950C February 2018 351
Manual Command
Set to the current CV output while the PID block is in Automatic
mode. When the block is switched to Manual mode, this value is used
to set the CV output and the internal value of the integral term within
the Upper and Lower Clamp and Slew Time limits.
Tracks CV in
Auto or sets
CV in Manual
Control Word
If the Override bit (bit 0) is set to 1, the Control Word and the internal
SP, PV and CV parameters must be used for remote operation of the
PID block (see below). This allows a remote operator interface device,
such as a computer, to take control away from the application
program.
Caution
If you do not want to allow remote
operation of the PID block, make
sure the Control Word is set to 0. If
the low bit is 0, the next 4 bits can be
read to track the status of the PID
input contacts as long as the PID
Enable contact has power.
Control Word is a discrete data structure with the first five bit
positions defined in the following format:
Status or
External Action if Override bit is set to 1:
If 0, monitor block contacts below. If 1, set
them externally.
If 1, block is in Manual mode. If other
numbers, it is in Automatic mode.
Should normally be 1. Otherwise block is
never called.
If 1 and Manual (Bit 1) is 1, CV is incremented
every solution.
If 1 and Manual (Bit 1) is 1, CV is decremented
every solution.
Maintained
by the CPU,
unless bit 0
(Override)
is set to 1.
Internal SP
Tracks the SP input. If Override = 1, must be set externally to solve the
PID algorithm using an alternate SP value. The original SP value is
maintained until overwritten.
Set and
maintained
by the CPU,
unless bit 0
(Override) of
Control
Word is set
to 1.
Non-
configurable,
unless bit 0
(Override) of
Control Word
is set to 1.
Internal CV
Tracks CV output.
Set and
maintained
by the CPU.
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