Mitsubishi Electric MELSEC iQ-R Series Programming Manual page 30

Control cycle (CT)
A control cycle is the cycle in which the loop control operation is performed.
Set an integral multiple of the execution cycle as the control cycle for each tag. The execution cycles are counted, and the
loop control operation is performed when the specified number of control cycles is reached.
Ex.
When the control cycle of M+M_PID is 1s in the program block with the execution cycle of 200ms
Program block (ΔT = 200ms)
Input
PVN
CASIN
(1) The IN function, PHPL function, and OUT1 function of M+M_PID are executed every 200ms. The PID function is not executed and the last value is used for
an output to OUT1.
(2) The IN function, PHPL function, PID function, and OUT1 function of M+M_PID are executed.
If the control cycle is not the integral multiple of execution cycle, round off the number after the decimal point of control cycle
(CT)  execution cycle (T) and multiply the execution cycle to calculate the control cycle.
For example, when the execution cycle (T) is 1.0s and the control cycle (CT) is 2.5s, the calculation is 2.5  1.0 = 2.5  3.
Therefore, the control cycle is 3s.
1 PROCESS CONTROL FUNCTION BLOCK
28
1.5 Program Execution Control
IN function PHPL function
(M+P_IN) (M+P_PHPL)
200ms
ΔT
(1) (1) (1)
CT
M+M_PID
PID function
(M+P_PID)
(1)
(2)
1s
MVN
OUT1 function
(M+P_OUT1)
CASOUT
CASOUT_T
(2)
Output