The program logic in the Series 90-20, 90-30, and Micro PLCs performs frequently until ended by a control from the programmer or a command from other device. The operations sequence required to implement a program a time is called a sweep. Additionally to performing the program logic, the sweep contains attaining data from input devices, transferring data to output devices, executing internal housekeeping, servicing other communications, and servicing the programmer. Series 90-20, 90-30, and Micro PLCs usually run in mode of STANDARD PROGRAM SWEEP.
Other modes of operating contain mode of STOP WITH I/O DISABLED, mode of STOP WITH I/O ENABLED, and mode of CONSTANT SWEEP. Every mode is managed by application configuration and external events settings. The PLC creates the decision concerning its mode of operating at the beginning of every sweep.
Standard Program Sweep
This mode usually works under all situations. The CPU works by executing a program of application, I/O updating, and communications performing and other jobs. This happens in a recurring cycle called the sweep of CPU. There are 7 parts to the sequence of implementation the Standard Program Sweep:
1. Housekeeping of start-of-sweep
2. Scan input (read inputs)
3. Solution of application program logic
4. Scan output (update outputs)
5. Communications programmer
6. Communications system
All steps carry out every sweep. Even though the Programmer Communications Window releases each sweep, programmer repairs only happen if a board error has been sensed or if the programming machine concerns a service request; the Programmer Communications Window First checks for operate to perform and ways out if there is none.
1. The contribution of scan time external service of device is dependent upon the communications window mode in which the service is routed. A maximum of 8 ms for the CPUs of 311, 313, 323, and 331 and 6 ms for the 340 and higher CPUs will be used up during that window if the mode of window is LIMITED. If the mode of window is RUN-TO-COMPLETION, a max. of 50 milliseconds can be used up in that window, depending upon the requests number which are offered concurrently.
2. These dimensions were taken with the physically of PCM nearby but not organized and with no application job operating on the PCM.
3. The words number check summed every sweep can be adjusted with the function block of SVCREQ.
4. These dimensions were taken with the default configuration and an empty program. The PLCs Series 90-30 were in an bare 10-slot rack with no addition racks linked. Also, the times presume that there is no interrupted active subroutine; the times will be longer if a subroutine periodic is active.
5. The time of data input for the Micro PLC can be decided as follows: 0.365 millsecs (fixed scan) + 0.036 millisecs (filter time) x (total sweep time) / 0.5millisecs.
6. Because the Micro PLC has a fixed I/O set, reconfiguration is not required.
7. Because the program user for the Micro PLC is in memory of Flash, it will not be confirmed for honesty.
GE Fanuc PLC
GE Fanuc PLC