User`s manual
41
FX3U Series Programmable Controllers
User’s Manual - MODBUS Serial Communication Edition
7 MODBUS Standard Commands
7.1 MODBUS Standard Commands Support List
1
Outline
2
Specifications
3
System
Configuration
4
Wiring
5
Communication
Setup
6
Related
Devices and
Comm. Status
7
MODBUS
Standard
Commands
8
Master
Specification
9
Slave
Specification
10
Creating
Programs
7. MODBUS Standard Commands
The following chapter explains in detail MODBUS Communication. For standard use of the FX3U MODBUS
Serial function please refer to Chapter 8 (Master Specification) or Chapter 9 (Slave Specification).
7.1 MODBUS Standard Commands Support List
The following table indicates a list of the MODBUS standard functions supported by the FX-Series MODBUS
Communication ADP.
Command
Code
Subcommand
Code
Command Name Details
Accessible
Devices per
Message
Broadcast Reference
0x01 Read Coils
Read binary (R/W)
devices
1 to 2000
points
✘ Section 7.4
0x02
Read Discrete
Inputs
Read binary (RO)
devices
1 to 2000
points
✘ Section 7.5
0x03
Read Holding
Registers
Read 16 bit (R/W)
register
1 to 125
points
✘ Section 7.6
0x04
Read Input
Registers
Read 16 bit (RO)
register
1 to 125
points
✘ Section 7.7
0x05 Write Single Coil
Write single binary
device
1 point ✔ Section 7.8
0x06
Write Single
Register
Write single 16 bit
register device
1 point ✔ Section 7.9
0x07
Read Exception
Status
Read 1 byte of
vendor specified
data
- ✘ Section 7.10
0x08
Diagnosis
0x00 Return Query Data
Loop back
function
- ✘
Subsection
7.11.1
0x01
Restart
Communication
Option
Restart
communication/
Remote
Communication
Reset
- ✔
Subsection
7.11.2
0x02
Return Diagnostic
Register
Read 16 bit
register of vendor
specified data
- ✘
Subsection
7.11.3
0x03
Change ASCII Input
Delimiter
Change ASCII
mode End of
Message
character
- ✔
Subsection
7.11.4
0x04
Force Listen Only
Mode
Switch slave to
Listen Only Mode
- ✔
Subsection
7.11.5
0x0A
Clear Counters and
Diagnostic Register
Clear all counters
and the diagnostic
registers
- ✔
Subsection
7.11.6
0x0B
Return Bus
Message Count
Read number of
detected
messages
- ✘
Subsection
7.11.7