User`s manual

61
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
7.11.5 Force listen only mode (sub-command code: 0x04)
Places a slave into the offline mode.
Used when disconnecting a slave from the network.
When FX-Series MODBUS Communication ADP is set in the listen only mode, the status is as follows:
• Ignores all request messages except for those of restart communications option (Refer to Subsection
7.11.2).
• Stops counting of the diagnostic counter (Refer to Chapter 6).
• Continues recording with the communications event log (Refer to Section 9.5).
1) Request message format (Master → Slave)
2) Response message format (Slave → Master)
(When completed normally)
No response message is returned because the listen only mode (offline status) is active.
(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.
Note
1) Whether the FX-Series MODBUS Communication ADP has been switched to listen only mode or not is
indicated by M8404/M8424.
2) The listen only mode can be changed to online mode by either of the following:
- Restart communications option (Refer to Subsection 7.11.2)
- Power OFF ON
(L)
Data
(L)
Function code
Function
code
(08
H)
Sub-function code
Sub-function code
(0004
H)
(0000
H)
(H)
(H)
Data
Function code
Function
code
(88
H)
Exception
code*
1