A-4-1 Plc Memory Addresses; A-4 Memory Map Of Plc Memory Addresses - Omron CJ2 CPU UNIT SOFTWARE User Manual

Appendices
A-4 Memory Map of PLC Memory
Addresses
A-4-1 PLC Memory Addresses
PLC memory addresses are set in Index Registers (IR00 to IR15) to indirectly address I/O memory.
Normally, use the MOVE TO REGISTER (MOVR(560)) and MOVE TIMER/COUNTER PV TO REGIS-
TER (MOVRW(561)) instructions to set PLC memory addresses into the Index Registers.
Some instructions, such as DATA SEARCH (SRCH(181)), FIND MAXIMUM (MAX(182)), and FIND
MINIMUM (MIN(183)), output the results of processing to an Index Register to indicate an PLC memory
address.
There are also instructions for which Index Registers can be directly designated to use the PLC mem-
ory addresses stored in them by other instructions. These instructions include DOUBLE MOVE
(MOVL(498)), some symbol comparison instructions (=L,<>L, <L, >L,<=L, and >=L), DOUBLE COM-
PARE (CMPL(060)), DOUBLE DATA EXCHANGE (XCGL(562)), DOUBLE INCREMENT BINARY
(++L(591)), DOUBLE DECREMENT BINARY (--L(593)), DOUBLE SIGNED BINARY ADD WITHOUT
CARRY (+L(401)), DOUBLE SIGNED BINARY SUBTRACT WITHOUT CARRY (-L(411)), SET
RECORD LOCATION (SETR(635)), and GET RECORD LOCATION (GETR(636)).
The PLC memory addresses all are continuous and the user must be aware of the order and bound-
aries of the memory areas. As reference, the PLC memory addresses are provided in a table at the end
of this appendix.
Precautions for Correct Use Precautions for Correct Use
Directly setting PLC memory addresses in the program should be avoided whenever possible. If
PLC memory addresses are set in the program, the program will be less compatible with new
CPU Unit models or CPU Units for which changed have been made to the layout of the memory.
Precautions for Correct Use Precautions for Correct Use
Address Offset and Array Variable Precautions
When using the following functions, a PLC memory address in the next data area may be speci-
fied depending on the offset value.
• When using an offset to indirectly specify an address.
• When indirectly specifying an element number in an array variable.
Be sure to program so that the data area is not exceeded, or consider the distribution order of
the data area of this memory map when programming.
A-164 CJ2 CPU Unit Software User's Manual