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10 PID CONTROL INSTRUCTIONS
10.2 PID Control Instructions (Inexact Differential)
• The S(P).PIDCONT instructions measure the sampling cycle and perform PID operation.
• Based on the setting value (SV) and process value (PV) in the I/O data area allocated to the device number specified by (s)
and later, these instructions perform PID operation and store the operation result in the automatic manipulated value (MV)
area in the I/O data area.
• The S(P).PIDCONT instructions perform PID operation when it is executed for the first time after a lapse of the specified
sampling cycle.
• During PID control, be sure to turn on the control command to allow the S(P). PIDCONT instruction to be executed every
scan. Failure to execute the instruction every scan disables PID operation in normal sampling cycles. The S(P).PIDCONT
instruction cannot be executed more than once in a single scan. Executing the instruction more than once in a single scan
disables PID operation in normal sampling cycles.
• The S(P).PIDCONT instruction cannot be written and used in interrupt programs. Writing an S(P).PIDCONT instruction in
the interrupt program disables PID operation in normal sampling cycles.
• In (s), specify the head of the device number specified in the I/O data area. ( Page 1155 I/O data)
• If a file register is specified as an I/O data area, do not apply memory protection for the file register. If memory protection is
applied, normal PID operation is disabled although no error results.
• The I/O data are assigned as follows.
*1 m=(n-1)23+10
• The number of device points used for I/O data setting is calculated by the following formula.
Number of device points = 10 + +23 n (n: number of loops used)
• Specify each data in binary.
• The initial processing flag sets the processing to be performed at the start of PID operation.
Item I/O data
Write (s)+0 Initial processing flag
Read/write disabled (s)+1
(s)+9
Work area for PID control
(system use only)
I/O data area for loop
No.1
(23 words)
Write (s)+10 Set value (SV)
(s)+11 Process value (PV)
Read (s)+12 Automatic manipulated value (MV)
(s)+13 Process value after filtering (PVf)
Write (s)+14 Manual manipulated value (MV
MAN
)
(s)+15 Manual/automatic selection (MAN/AUTO)
Read/write (s)+16 Alarm (ALARM)
Read/write disabled (s)+17
(s)+32
Work area for loop No.1
(system use only)
I/O data area for loop
No.n
(23 words)
*1
Write (s)+(m+0) Set value (SV)
(s)+(m+1) Process value (PV)
Read (s)+(m+2) Automatic manipulated value (MV)
(s)+(m+3) Process value after filtering (PVf)
Write (s)+(m+4) Manual manipulated value (MV
MAN
)
(s)+(m+5) Manual/automatic selection (MAN/AUTO)
Read/write (s)+(m+6) Alarm (ALARM)
Read/write disabled (s)+(m+7)
(s)+(m+22)
Work area for loop No.n
(system use only)
• Initial operation processing is performed assuming that the sampling cycle that has been set has been reached.
• If the initial processing flag is 0, PID operations for the number of loops used are performed altogether in a single scan. If it is not 0, PID operations for the
number of loops used are divided and processed in several scans, and sampling is started sequentially from the loop that has completed initial processing.
The number of processing loops per scan is the number of execution loops per scan that has been set.
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