User`s manual

FX3U Series Programmable Controllers

User’s Manual - MODBUS Serial Communication Edition

7 MODBUS Standard Commands

7.11 Diagnostics (Command Code: 0x08)

7.11.2 Restart communications option (sub-command code: 0x01)

Initializes the communication port of the receiving channel side and restarts the slave function.

Restart is performed after returning the response message corresponding to a request

message.

The operation status returns to online mode when it was in the listen only mode.

The following data are cleared when executing the restart communications option.

• Event and Error counter (Refer to Chapter 6)

• Communications event log (Refer to Section 9.5)

*1. Clears the data when the communications event log clear is specified in the request message.

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.

However, if a request message is received during listen only mode, the status will only return to online

mode and no response message will be returned.

(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)

Data

(L)

Function

code

(08

Function code

Sub-function code

(0001

Clear setting of

Communications event log

0000

H: Do not clear

FF00

H: Clear

(H)

Data

Function code

Function

code

(88

Exception

code*