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Chapter 7. PID Built-In Function Block
Words
18
Internal PV
(Address+17)
Tracks PV input. Must be set externally if Override bit is set to 1.
19
Output
(Address+18)
A Signed word value representing the output of the function block
before the optional inversion. If the output polarity bit in the Config
Word is set to 0, this value equals the CV output. If the output polarity
bit is set to 1, this value equals the negative of the CV output.
20
Derivative Term Storage
(Address+19)
Used internally for storage of intermediate values. Do not write to this
location.
21, 22
Integral Term Storage
(Address+20.
Used internally for storage of intermediate values. Do not write to
Address+21)
these locations.
23
Slew Term Storage
(Address +22)
Used internally for storage of intermediate values. Do not write to this
location.
24 – 26
Previous Solution Time
(Address+23
Internal storage of time of last PID solution. Normally do not write to
–
these locations. Some special circumstances may justify writing to
Address+25)
these locations.
Note:
If you call the PID block in Automatic mode after a long delay,
you might want to use SVC_REQ #16 or SVC_REQ #51 to load
the current CPU elapsed time clock into Word 24 to update
the last PID solution time to avoid a step change of the
integral term.
27
Integral Remainder Storage
(Address+26)
Holds remainder from integral term scaling.
28, 29
SP, PV Lower Range
(Address+27,
SP, PV Upper Range
Address+28)
Optional integer values in PV Counts that define high and low display
values for SP and PV. (Word 29 must be greater than word 28.)
30
Reserved
(Address+29)
Word 30 is reserved. Do not use this location.
31, 32
Previous Derivative Term Storage
(Address+30,
Used in calculations for derivative filter. Do not write to these
Address+31)
locations.
33 – 40
Reserved
(Address+32
Words 32-39 are reserved. Do not use these references.
–
Address+39)
352
PACSystems* RX7i, RX3i and RSTi-EP CPU Programmer's Reference Manual
Parameter/Description
Low Bit
Range
Units
Set and
Non-
maintained
configurable,
by the CPU,
unless bit 0
unless bit 0
(Override) of
(Override) of
Control
Control Word
Word is set
is set to 1.
to 1.
Set and
Non-
maintained
configurable.
by the CPU.
Set and
Non-
maintained
configurable.
by the CPU.
Set and
Non-
maintained
configurable.
by the CPU.
PV
-32768 to
Counts
32767
N/A
Non-
configurable.
Set and
Non-
maintained
configurable.
by the CPU.
N/A
Non-
configurable
GFK-2950C
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