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170
Index Registers
Section 4-15
CPU Bus Units (D30000 to D31599)
Each CPU Bus Unit is allocated 100 words (based on unit numbers 0 to F).
Refer to the Unit’s operation manual for details on the function of these words.
With some CPU Bus Units such as Ethernet Units, initial settings must be reg-
istered in the CPU Unit’s Parameter Area; this data can be registered with the
CX-Programmer.
■
DM Fixed Allocation Words for Modbus-RTU Easy Master
The following DM area words are used as command and response storage
areas for the Modbus-RTU Easy Master function.
D32200 to D32299: Serial port 1
D32300 to D32399: Serial port 2
For use of these areas, refer to
6-1-3 Modbus-RTU Easy Master Function
.
4-15 Index Registers
The sixteen Index Registers (IR0 to IR15) are used for indirect addressing.
Each Index Register can hold a single PLC memory address, which is the
absolute memory address of a word in I/O memory. Use MOVR(560) to con-
vert a regular data area address to its equivalent PLC memory address and
write that value to the specified Index Register. (Use MOVRW(561) to set the
PLC memory address of a timer/counter PV in an Index Register.)
Note
Refer to
Appendix E Memory Map
for more details on PLC memory
addresses.
Indirect Addressing
When an Index Register is used as an operand with a “,” prefix, the instruction
will operate on the word indicated by the PLC memory address in the Index
Register, not the Index Register itself. Basically, the Index Registers are I/O
memory pointers.
• All addresses in I/O memory (except Index Registers, Data Registers, and
Condition Flags) can be specified seamlessly with PLC memory
addresses. It isn’t necessary to specify the data area. I/O memory
addresses for IR, DR, and Condition Flags, however, cannot be held.
• In addition to basic indirect addressing, the PLC memory address in an
Index Register can be offset with a constant or Data Register, auto-incre-
mented, or auto-decremented. These functions can be used in loops to
read or write data while incrementing or decrementing the address by one
each time that the instruction is executed.
DM Area for CPU Bus Units
(100 words/Unit)
CPU Unit
Special I/O Unit
Data trans-
ferred to the
CJ Unit when
the PLC is
turned ON or
the Unit is
restarted.
Data trans-
ferred to the
CPU Unit at
cyclic refresh-
ing or when
necessary.
Summary of Contents for CP1H CPU UNITS - PROGRAMMING 05-2007
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Page 3: ...CP1H X40D CP1H XA40D CP1H Y20DT D CP1H CPU Unit Operation Manual Revised March 2009...
Page 4: ...iv...
Page 10: ...x...
Page 18: ...xviii...
Page 22: ...xxii...
Page 34: ...xxxiv Conformance to EC Directives 6...
Page 174: ...140 CP series Expansion I O Unit Wiring Section 3 6...
Page 370: ...336 Analog I O XA CPU Units Section 5 5...
Page 552: ...518 Trouble Shooting Section 8 7...
Page 595: ...561 Sample Application Section 9 12 Network Settings Network Tab Network Settings Driver Tab...
Page 598: ...564 Sample Application Section 9 12...
Page 642: ...608 Standard Models Appendix A...
Page 652: ...618 Dimensions Diagrams Appendix B...
Page 745: ...711 Connections to Serial Communications Option Boards Appendix F Connecting to Unit...
Page 746: ...712 Connections to Serial Communications Option Boards Appendix F...
Page 776: ...742 PLC Setup Appendix G...
Page 778: ...744 Specifications for External Power Supply Expansion Appendix H...
Page 786: ...752 Revision History...