Mitsubishi Electric MELSEC-Q series Programming Manual page 64

[FUNCTION]
• When the S(P).PIDCONT instruction is executed, the sampling cycle is measured and PID operation is performed.
• With the S(P).PIDCONT instruction, PID operation is carried out on the basis of the set value (SV) and process value (PV)
in the I/O data area set to the device number specified by
automatically manipulated value (MV) area of the I/O data area.
• PID operation is executed in response to the execution of the S(P).PIDCONT instruction appearing first after the set time
for sampling cycle has elapsed. ( Page 50 Sampling cycle)
• During PID control, turn ON the control command to execute the S(P).PIDCONT instruction in every scan. If not, PID
operation in a normal sampling cycle will not available. It is not possible to execute the S(P).PIDCONT instruction more
than once in one scan. If it is executed more than once in one scan, PID operation cannot be performed in a normal
sampling cycle.
• The S(P).PIDCONT instruction is not available for use in an interrupt program, fixed scan execution type program or low
speed execution type program. If the S(P).PIDCONT instruction has been used in an interrupt program, fixed scan
execution type program or low speed execution type program, PID operation cannot be performed in a normal sampling
cycle.
• For , designate the first number of the device numbers that are designated in the I/O data area. If file registers (R) are
S
designated for the I/O data area, do not set memory protect ON for the file registers (R). If memory protect is set ON,
correct PID operation will be precluded, although no error will occur. ( Page 51 I/O Data)
• Execute the S(P).PIDCONT instruction in every scan even while the manual manipulated value (MV
the manual control mode. The bumpless switching cannot be executed if the S(P).PIDCONT instruction has not been
executed. ( Page 31 Bumpless changeover function)
• Use the READY signal to establish an interlock with respect to the individual modules, so that the S(P).PIDCONT
instruction is executed only when both the A/D converter module for reading the PV (process value) and the D/A converter
module for outputting the MV (manipulated value) are normal. If the S(P).PIDCONT instruction is executed while either or
both of the modules are faulty, PID operation cannot be executed correctly because the PV (process value) cannot be read
correctly and/or the MV (manipulated value) cannot be output correctly.
[OPERATION ERRORS]
An operation error will occur, the error flag (SM0) will be turned ON, and an error code will be stored in SD0, in the following
cases.
Error code Description
4103 When the S(P).PIDINIT instruction is not executed before executing the S(P).PIDCONT instruction.
4100 When the value set as the PID control data is outside the allowable range.
4101 When the device range allocated to the PID control data area, designated with
device.
For details on the READY signals of the A/D converter module and D/A converter module, refer to the manual for the relevant
module.
8 INCOMPLETE DERIVATIVE PID CONTROL INSTRUCTIONS AND PROGRAM EXAMPLES
62
8.1 PID Control Instructions
or later, and the operation result is stored into the
S
, exceeds the last device number of the corresponding
S
) is being output in
MAN