User`s manual

63
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
7.11.7 Return bus message count (sub-command code: 0x0B)
Reads out the number of messages detected on the line to the master.
1) Request message format (Master → Slave)
2) Response message format (Slave → Master)
(When completed normally)
*1. Refer to Chapter 6 for the relevant counts, count clear methods and precautions.
(When completed with an error)
*2. 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)
Function code
Function
code
(08
H)
Data
(L)
Sub-function code
Sub-function code
(000B
H)
(0000
H)
(H) (H)
(L)
Data
(L)
Function code
Function
code
(08
H)
Sub-function code
Sub-function code
(000B
H)
Bus message count value
(0000
H to FFFFH) *
1
(H)
(H)
Data
Function code
Function
code
(88
H)
Exception
code *
2