128
Index Registers
Section 4-11
Setting Index Registers
Always set the required value in an index register before using it. The con-
tents of an index register will be unpredictable if it is not set in advance.
The contents of an index register is also unpredictable after an interrupt task
is started. When using index registers inside an interrupt task, use
MOVR(560) (for anything but timer/counter PVs) or MOVRW(561) (for
timer/counter PVs) to set the required value.
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)
Summary of Contents for CP1L-EL20DR-D
Page 3: ...CP1L EL20D CP1L EM30D CP1L EM40D CP1L EL EM CPU Unit Operation Manual Produced July 2017...
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Page 10: ...x...
Page 22: ...xxii...
Page 34: ...xxxiv Software Licenses and Copyrights 7...
Page 192: ...158 Trial Operation and Debugging Section 5 3...
Page 250: ...216 Automatic Clock Adjustment and Specifying Servers by Host Name Section 6 7...
Page 666: ...632 Trouble Shooting Section 11 7...
Page 696: ...662 Standard Models Appendix A...
Page 805: ...771 Connections to Serial Communications Option Boards Appendix F Connecting to Unit...
Page 806: ...772 Connections to Serial Communications Option Boards Appendix F...
Page 836: ...802 PLC Setup Appendix G...
Page 838: ...804 TCP Status Transitions Appendix H...
Page 840: ...806 Ethernet Network Parameters Appendix I...
Page 842: ...808 Buffer Configuration CP1L EL EM Appendix J...
Page 844: ...810 Ethernet Specifications Appendix K...
Page 851: ...Index 817 work words 118 write protection 447...
Page 852: ...818 Index...
Page 854: ...820 Revision History...
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