CJ2 CPU Unit Software User's Manual - CIP ETI

8 I/O Allocations and Unit SettingsPrecautions for Correct UseIORF(097), FIORF(225), IORD (222), and IOWR(223) can be executed for Special I/O Unitsfrom interrupt tasks. When doing so, always disable the Special I/O Unit's cyclic refreshing in thePLC Setup. If cyclic refreshing is not disabled and either of the following processes is executed inan interrupt task, a non-fatal error will occur and the Duplicate Refresh Error Flag (A402.13) willturn ON.• I/O refreshing is executed using IORF(097) or FIORF(225) for the same Special I/O Unit.• Data is read or written to or from the memory area using IORD (222) or IOWR(223) for thesame Special I/O Unit.Whenever disabling a Special I/O Unit's cyclic refreshing, be sure that the I/O for that Unit isrefreshed with IORF(097) or FIORF(225) in the program at least every 11 seconds during operation.A CPU Unit service monitoring error will occur in the Special I/O Unit if it is not refreshedevery 11 seconds.CPU Bus Units CPU Bus Unit Area (I/O Refreshing)Data is exchanged each cycle during I/O refreshing of the CPU Bus Unit Area. Basically, 25 wordsare allocated to each CPU Bus Unit based on its unit number setting. The number of words actuallyused by the CPU Bus Unit varies.The Special I/O Unit Area ranges from CIO 1500 to CIO 1899 (25 words × 16 Units).CPU UnitCPU Bus UnitCPU Bus Unit Area25 words/UnitTransferredinI/OrefreshingNote The CPU BUS I/O REFRESH instruction (DLNK(226)) can be executed in the ladder program to refresh theCIO Area words allocated to the CPU Bus Unit of a specified unit number. Transfer of Words Allocated in the DM AreaOne hundred words are allocated to each Unit according to the unit number.Note These words are not used for all models of CPU Bus Unit.DM Area Words for the CPU Bus Units: D30000 to D31599 (100 words × 16 Units)The contents of these words are transferred at the following times. Which transfers actually takeplace depends on the model of the Unit.• Data transferred when the PLC is turned ON.• Data transferred each cycle.• Data transferred when necessary.Note The CPU BUS I/O REFRESH instruction (DLNK(226)) can be executed in the ladder program to refresh theDM Area words allocated to the CPU Bus Unit of a specified unit number.Some models transfer data in both directions, from the DM Area to the Unit and from the Unit to theDM Area. Refer to the Unit's operation manual for details on data transfers.8-26 CJ2 CPU Unit Software User’s Manual