CJ2 CPU Unit Software User's Manual - CIP ETI

5 Understanding Programming5-5-8 Automatic Address Allocation to SymbolsWhen programming, you can automatically allocate addresses to symbols. Select Memory Allocation− Automatic Address Allocation from the PLC Menu in the CX-Programmer and then set the rangeand data type for automatic allocation. With CJ2 CPU Units, addresses in the CIO Area, Auxiliary Area,Holding Area, Work Area, DM Area, or EM Area can be allocated.When automatically allocating symbol addresses in the EM Area, we recommend used the requirednumber of banks starting backward from the highest EM Area bank.The following example shows the settings to automatically allocate symbol addresses in banks 17 and18 hex of a CJ2H-CPU68-EIP CPU Unit (which has EM Area banks from 00 to 18 hex).55-5 SymbolsRefer to the CX-Programmer Operation Manual (Cat. No. W446) for details on the area settings forautomatic address allocation.Additional Information• With CJ2H CPU Units, bits in EM Area banks that are set for automatic address allocation canbe force-set/reset. Refer to 6-14 Extended Data Memory Area for the banks in which bits canbe force-set/reset.• Automatic address allocation is not possible for structure variables.Precautions for Safe Use5-5-8 Automatic Address Allocation to SymbolsData in the EM Area is backed up when the power supply is turned OFF or the operating mode ischanged. Be careful when using output bits specified as BOOL data. If necessary, including programmingto clear memory as required.Example: The following instructions can be used to clear bank 18 hex to all zeros when power isturned ON when EM Area bank 18 hex is set for automatic address allocation.First Cycle FlagBSET(071)#0000E18_0E18_32767CJ2 CPU Unit Software User’s Manual5-59