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Index Registers Section 9-17
Since some operands are treated as word data and others are treated as bit
data, the meaning of the data in an Index Register will differ depending on the
operand in which it is used.
1,2,3... 1. Word Operand:
MOVR(560) 0000 IR2
MOV(021) D00000 , IR2
When the operand is treated as a word, the contents of the Index Register
are used “as is” as the PLC memory address of a word.
In this example MOVR(560) sets the PLC memory address of CIO 0002 in
IR2 and the MOV(021) instruction copies the contents of D00000 to
CIO 0002.
2. Bit Operand:
MOVR(560) 000013 ,IR2
SET +5 , IR2
When the operand is treated as a bit, the leftmost 7 digits of the Index Reg-
ister specify the word address and the rightmost digit specifies the bit num-
ber. In this example, MOVR(560) sets the PLC memory address of
CIO 000013 (0C000D hex) in IR2. The SET instruction adds +5 from bit 13
to this PLC memory address, so it turns ON bit CIO 000102.
Direct Addressing When an Index Register is used as an operand without a “,” prefix, the instruc-
tion will operate on the contents of the Index Register itself (a two-word or
“double” value). Index Registers can be directly addressed only in the instruc-
tions shown in the following table. Use these instructions to operate on the
Index Registers as pointers.
The Index Registers cannot be directly addressed in any other instructions,
although they can usually be used for indirect addressing.
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.
Instruction group Instruction name Mnemonic
Data Movement
Instructions
MOVE TO REGISTER MOVR(560)
MOVE TIMER/COUNTER PV TO REG-
ISTER
MOVRW(561)
DOUBLE MOVE MOVL(498)
DOUBLE DATA EXCHANGE XCGL(562)
Table Data Processing
Instructions
SET RECORD LOCATION SETR(635)
GET RECORD NUMBER GETR(636)
Increment/Decrement
Instructions
DOUBLE INCREMENT BINARY ++L(591)
DOUBLE DECREMENT BINARY – –L(593)
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)
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