User`s manual

57
FX3U Series Programmable Controllers
User’s Manual - MODBUS Serial Communication Edition
7 MODBUS Standard Commands
7.11 Diagnostics (Command Code: 0x08)
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
7.11 Diagnostics (Command Code: 0x08)
Executes the various diagnostics and checks the FX-Series MODBUS Communication ADP.
7.11.1 Return query data (sub-comand code: 0x00)
Returns the contents of the request message without change.
Used to check if the network or the target device is operating normally. (Loopback test)
1) Request message format (Master → Slave)
2) Response message format (Slave → Master)
(When completed normally)
The slave returns the request message received from the master without change.
(When completed with an error)
*1. Exception and error codes are stored in special data registers and special auxiliary relays in the case
of error completion. Refer to Chapter 6 for storage location, confirmation methods, and other detailed
contents.
(L)
Data
Function code
Function
code
(08
H)
Sub-function code
Sub-function code
(0000
H)
Arbitrary data
(H)
Data
Function code
Function
code
(88
H)
Exception
code*
1