CJ2 CPU Unit Software User's Manual - CIP ETI

3 CPU Unit OperationPeripheral ServicingPeripheral servicing involves servicing non-scheduled events for external devices. This includes bothevents from external devices and service requests to external devices.Most peripheral servicing for CJ-series PLCs involves FINS commands. The amount of time specifiedin the system is allocated to each type of servicing and executed every cycle. If all servicing cannot becompleted within the allocated time, the remaining servicing is performed the next cycle. If peripheralservicing is delayed too much, increase the fixed servicing time in the PLC Setup to a value larger than10% using the CX-Programmer. Peripheral Servicing TimeWith the default peripheral servicing time setting, 10% of the preceding cycle time is assigned to thetotal peripheral service. Therefore, the peripheral servicing time depends on the preceding cycletime.Set a time longer than 10% of the cycle time using Fixed Servicing Time in the PLC Setup from theCX-Programmer when peripheral servicing is delayed because too many cycles is required to completeit. Keep in mind that increasing the servicing time will also increase the cycle time. Types of Peripheral ServicingUnitsEvent servicing for Special I/O UnitsEvent servicing for CPU Bus UnitsPeripheral USB port serviceSerial port serviceCommunications port servicingFile access servicingOnline editing servicingBackup servicingServicing• Non-scheduled servicing for FINS commands from Special I/O Unitsand CPU Bus Units (e.g., requests to start external interrupt tasks)• Non-scheduled servicing for FINS commands from the CPU Unit to theabove Units.• Non-scheduled servicing for FINS or Host Link commands received viathe peripheral USB or serial ports from Programming Devices, PTs, orhost computers (e.g., requests to transfer programming, monitoring,forced-set/reset operations, or online editing)• Non-scheduled servicing from the CPU Unit transmitted from the peripheralUSB or serial port (non-solicited communications)• Servicing to execute network communications, serial communications,or file memory access for the SEND(090)/SEND2(491),RECV(098)/RECV2(492), CMND(490)/CMND2(493), orPMCR(260)/PMCR2(264) instructions using communications ports(internal logic ports).• Servicing to execute background execution using communications ports.File read/write operations for Memory Cards or EM file memory.Servicing to backup contents edited with online editing in the built-in flashmemory when online editing is being processed.Servicing to backup changed contents in the built-in flash memory whenthere is a change in programming or parameters.33-1 CPU Unit Internal Operation3-1-2 Cycle TimeAdditional InformationServicing time is allocated to Special I/O Units, CPU Bus Units, the peripheral USB port, serialports, file access, and communications ports.If servicing is separated over many cycles, delaying completion of the servicing, set the sameallocated time (same time for all services) rather than a percentage under execute time settingsin the PLC Setup.CJ2 CPU Unit Software User’s Manual3-5