Chapter 7. PID Built-In Function Block354 PACSystems* RX7i, RX3i and RSTi-EP CPU Programmer's Reference Manual GFK-2950C7.3.3 Time Interval for the PID FunctionThe start time of each CPU sweep is used as the current time when calculating the time intervalbetween solutions of the PID function. The times and time intervals have a resolution of 100 μs.When an application uses multiple PID functions, all of them use the same time value.The PID algorithm is solved when the current time is equal to or greater than the time of the last PIDsolution plus the Sample Period or 10 ms; whichever is larger. If the Sample Period is set forexecution on every sweep (value = 0), the PID function is restricted to a minimum of 10 ms betweensolutions. If the sweep time is less than 10 ms, the PID function waits until enough sweeps haveoccurred to accumulate an elapsed time of at least 10 ms. For example, if the sweep time is 9 ms,the PID function executes every other sweep, and the time interval between solutions is 18 ms. If aspecific PID function is executed more than once per sweep (by referencing the same reference arraylocation in multiple PID function blocks), the algorithm is solved only on the first call.The longest possible interval between executions is 65,535 times 10 ms, or 10 minutes, 55.35seconds.
