Tips and Tricks5-2 PLC S7-300, CPU Specifications CPU 312 IFM to CPU 318-2 DPA5E00111190-01With Backup Battery Without Backup BatteryCPU program on MemoryCard or in the integralEPROM of the312IFM/314IFMMemory card not pluggedinAll DBs are retentive,whatever configuration hasbeen performed. The DBsgenerated using SFC 22“CREAT_DB” are alsoAll DBs (retentive,non-retentive) are transferredfrom the memory card or fromthe integral EPROM into RAMon restart.The DBs configured asretentive retain their contentsretentive. Data blocks or data areas you have generated withSFC22 ”CREAT_DB” are not retentive. After a power failure, the retentive data areas are retained.Note:These data areas are stored in the CPU, not on thememory card. The non-retentive data areas containwhatever has been programmed on EPROM.Watchdog Interrupt: Scan period > 5 msFor the watchdog interrupt, you should set a scan period > 5 ms. With lower valuesthe risk of frequent occurrence of watchdog interrupt errors increases, for example,depending on The program cycle time of an OB35 Frequency and program cycle time of higher priority classes Programming device functions.Hardware Interrupts Generated in I/O ModulesWhen using applications critical to hardware interrupt, insert thehardware-triggering modules as close to the CPU as possible.Reason: Interrupts generated in module rack 0, slot 4, are read first. The otherslots follow in ascending order.
