299
Modbus-RTU Slave Function for Replacing Existing PLCs
Section 9-6
Note
The differences between the command and response frames for 1:N Modbus-
RTU Slaves and 1:1 Modbus-RTU Slaves is as follows:
1:N Modbus-RTU Slave
• Command Format
• Response Format
1:1 Modbus-RTU Slave
The frame format for a 1:1 Modbus-RTU Slave is the same as that for the 1:N
Modbus-RTU Slave, except the @, Modbus-RTU Slave Unit No., and FCS are
omitted.
• Command Format
• Response Format
9-6-2
Modbus-RTU Slave-compatible Device Selection
Pre-Ver. 1.2 Units
In earlier models, when the host computer program used by the C-series
Modbus-RTU Slave Unit was reused in a CS/CJ-series PLC, data could not
be read normally for some programs due to the differences in Modbus-RTU
Slave specifications.
Modbus Data Models
Discrete Inputs
Coils
Input Registers
Holding Registers
1
2
3
:
1
2
3
:
1
2
3
:
1
2
3
:
CIO Area
Work Area
Holding Area
DM Area
0
1
2
:
0
1
2
:
0
1
2
:
0
1
2
:
EM Area
0
1
2
:
Modbus-RTU command
Modbus Commands
Read Coils
Read Discrete Inputs
Read Holding Registers
Read Input Registers
Write Single Coil
Write Single Register
Write Multiple Coils
Write Multiple Registers
DM Area settings are used to
allocate the area for each data
model except for discrete inputs.
I/O Memory
CS/CJ-series CPU Unit
× ×
* CR
Terminator
FCS
Host Link
Unit No.
Header
code
End
code
@ 0 0 R D 0 0
* CR
Terminator
Header code
R D
* CR
Header
code
End code
R D 0 0
Terminator
Summary of Contents for SYSMAC CJ1W-SCU21-V1
Page 3: ...iv...
Page 5: ...vi...
Page 9: ...x...
Page 15: ...xvi...
Page 89: ...60 Basic Operating Procedure Section 1 9...
Page 151: ...122 RS 232C and RS 422A 485 Wiring Section 3 4...
Page 173: ...144 Host Link Function for Replacing Existing PLCs Section 4 6...
Page 223: ...194 Enhanced Protocol Macro Functions Section 5 6...
Page 277: ...248 Communications Frames Section 6 8...
Page 291: ...262 Basic Operating Procedure in No protocol Mode Section 7 4...
Page 301: ...272 Auxiliary Area and CIO Area Allocations Section 8 3...
Page 391: ...362 Introduction Appendix A...
Page 421: ...392 CompoWay F Master Protocol Appendix B...
Page 513: ...484 E5 K Digital Controller Read Protocol Appendix F...
Page 571: ...542 E5ZE Temperature Controller Write Protocol Appendix I...
Page 587: ...558 E5 J Temperature Controller Protocol Appendix J...
Page 627: ...598 ES100 Digital Controller Protocol Appendix K...
Page 661: ...632 V500 V520 Bar Code Reader Protocol Appendix M...
Page 697: ...668 3Z4L Laser Micrometer Protocol Appendix N...
Page 717: ...688 Visual Inspection System Protocol Appendix O...
Page 755: ...726 V600 V620 ID Controller Protocol Appendix P...
Page 763: ...734 Hayes Modem AT Command Protocol Appendix Q...
Page 767: ...738 Changing Communications Port Settings Using STUP 237 Appendix R...
Page 781: ...752 Revision History...