129
Index Registers
Section 4-11
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)
Example:
If, for example, instruction A above is a comparison instruction, table data
could be read from start to the end of the table to compare all of the data with
a specific value. In this way, blocks of user-defined processing can be freely
created depending by applying Index Registers.
IR0
,IR0
Instruction execution
repeatedly incrementing
IR0 by 1
Instruction
Indirect
addressing
Table data
Instruction A
Instruction A m+1
Instruction A m+n
MOVR m IR0
The PLC memory address
of address m is stored in IR0.
Repeated execution,
e.g., loop for
FOR or NEXT.
Instruction A ,IR0+
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...
Page 4: ...iv...
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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