Chapter 7. PID Built-In Function Block
352
PACSystems* RX7i, RX3i and RSTi-EP CPU Programmer's Reference Manual
GFK-2950C
Words
Parameter/Description
Low Bit
Units
Range
18
(17)
Internal PV
Tracks PV input. Must be set externally if Override bit is set to 1.
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.
19
(18)
Output
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.
Set and
maintained
by the CPU.
Non-
configurable.
20
(19)
Derivative Term Storage
Used internally for storage of intermediate values. Do not write to this
location.
21, 22
(20.
21)
Integral Term Storage
Used internally for storage of intermediate values. Do not write to
these locations.
23
(A22)
Slew Term Storage
Used internally for storage of intermediate values. Do not write to this
location.
24
–
26
(23
–
25)
Previous Solution Time
Internal storage of time of last PID solution. Normally do not write to
these locations. Some special circumstances may justify writing to
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.
Set and
maintained
by the CPU.
Non-
configurable.
27
(26)
Integral Remainder Storage
Holds remainder from integral term scaling.
Set and
maintained
by the CPU.
Non-
configurable.
28, 29
(27,
28)
SP, PV Lower Range
SP, PV Upper Range
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.)
PV
Counts
-32768 to
32767
30
(29)
Reserved
Word 30 is reserved. Do not use this location.
N/A
Non-
configurable.
31, 32
(30,
31)
Previous Derivative Term Storage
Used in calculations for derivative filter. Do not write to these
locations.
Set and
maintained
by the CPU.
Non-
configurable.
33
–
40
(32
–
39)
Reserved
Words 32-39 are reserved. Do not use these references.
N/A
Non-
configurable
Summary of Contents for PACSystems RSTi-EP
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