The throughput time includes the time for actuation of the physical input ; time for PLC’s input circuit to sense the signal;time for input scan, program scan and output scan; time for actuation of the output circuit & corresponding field device;and time for the CPU’s housekeeping or overhead functions.
herefore the formula is --
Input scan time+Output scan time+housekeeping time+ program scan time(addition of instruction execution times when all instructions are True) +PLC input circuit filter time+PLC output circuit turn on time.
Advanced Micros offer functions of high speed counting with direct control of outputs & immediate I/O update instructions. These functions enable the micro controller to detect & react quickly to changing conditions.