452
FX
3U
/FX
3UC
Series Programmable Controllers
Programming Manual - Basic & Applied Instruction Edition
16 External FX Device – FNC 80 to FNC 89
16.7 FNC 88 – PID / PID Control Loop
Cautions
1. When using two or more PID instructions
Two or more PID instructions can be executed at the same time. (There is no limitation in the number of
loops.) However, make sure that
,
and other operands specified in each instruction are different
to each other.
2. Number of devices occupied for parameters starting from
1) In the limit cycle method
- Twenty-nine devices are occupied from the head device specified in
.
2) In the step response method
- Operation setting (ACT): When all of bits 1, 2 and 5 are any value other than "0"
Twenty-five devices are occupied from the head device specified in
.
- Operation setting (ACT): When all of bits 1, 2 and 5 are "0"
Twenty devices are occupied from the head device specified in
.
3. When specifying a device in the latch area backed up by the battery
For the output value (MV) in PID instruction, specify a data register (D) in the non-latch area.
(When specifying a data register in the latch area, make sure to clear the latched (battery backed) contents
when the PLC mode is set to RUN using the following program.)
Error
When an operation error occurs, the special auxiliary relay M8067 turns ON, and the error code is stored in
the special data register D8067.
→
For the error code, refer to Section 37.4.
S
3
D
S
3
S
3
S
3
S
3
M8002
Initial pulse
RST
D***
Program example
Data register number in the latch area specified in
D
