Omron CP1L - 4-11-1 Using Index Registers

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Index Registers Section 4-11
The SRCH(181), MAX(182), and MIN(183) instructions can output the PLC
memory address of the word with the desired value (search value, maximum,
or minimum) to IR0. In this case, IR0 can be used in later instructions to
access the contents of that word.
4-11-1 Using Index Registers
Processing of multiple (identical) instructions such as consecutive addresses
for table data can be merged into one instruction by combining repetitive pro-
cessing (e.g., FOR(513) and NEXT(514)instructions) with indirect addressing
using Index Registers, thereby simplifying programming.
The Index operation uses the following procedure.
1. PLC memory addresses for the addresses in the Index Registers are
stored using a MOVR instruction.
2. Operation is then executed by indirectly addressing Index Registers to the
operand for Instruction A.
3. The addresses are moved using processing such as adding, subtracting,
incrementing, or decrementing the Index Register (see note).
4. Steps 2 and 3 are processed repeatedly until the conditions are met.
Note Adding, subtracting incrementing, or decrementing for the Index
Register is performed using one of the following methods.
• Each Type of Indirect Addressing for Index Registers:
Auto-increment (,IR@+ or ,IR@++), auto-decrement (,-IR@ or ,--IR@),
constant offset (constant ,IR@), and DR offset (DR@,IR@) for Index
Registers
• Instructions for Direct Addressing of Index Registers:
DOUBLE SIGNED BINARY ADD WITHOUT CARRY (+L), DOUBLE
SIGNED BINARY SUBTRACT WITHOUT CARRY (-L), DOUBLE IN-
CREMENT BINARY (++L), DOUBLE DECREMENT BINARY (--L)
Comparison Instructions DOUBLE EQUAL =L(301)
DOUBLE NOT EQUAL < >L(306)
DOUBLE LESS THAN < L(311)
DOUBLE LESS THAN OR EQUAL < =L(316)
DOUBLE GREATER THAN > L(321)
DOUBLE GREATER THAN OR EQUAL > =L(326)
DOUBLE COMPARE CMPL(060)
Symbol Math Instructions DOUBLE SIGNED BINARY ADD WITH-
OUT CARRY
+L(401)
DOUBLE SIGNED BINARY SUBTRACT
WITHOUT CARRY
–L(411)
Instruction group Instruction name Mnemonic
IR0
,IR0
Instruction execution
repeatedly incrementing
IR0 by 1
Instruction
Indirect
addressing
Table data