Despatch Protocol Plus Modbus Communications User Manual

Page 35

Chromalox Instruments and Controls

A-51643 Rev. 6 10/06/03

Query

Response

Field Name

Data

Field Name

Data

Slave address

$02

Slave address

$02

Function

$08

Function

$08

Sub-function hi

$00

Sub-function hi

$00

Sub-function lo

$00

Sub-function lo

$00

Data hi

$AA

Data hi

$AA

Data lo

$55

Data lo

$55

CRC

$----

CRC

$----

5.3.1.2 [08 01] Restart Communications Option

The slave is reset, its communication port initialized and restarted, and all of its communications event

counters cleared. If the slave is currently in Listen Only mode, no response is returned. This function is

the only one that brings the port out of Listen Only mode. If the port is not currently in Listen Only

mode, a normal response is returned. This occurs before the reset is executed. When the slave receives

the query, it attempts a restart and executes its power-up confidence tests. Successful completion of the

tests will bring the port online.

Example: Restart Communications on slave device 2.

Query

Response

Field Name

Data

Field Name

Data

Slave address

$02

Slave address

$02

Function

$08

Function

$08

Sub-function hi

$00

Sub-function hi

$00

Sub-function lo

$01

Sub-function lo

$01

Data hi

$00

Data hi

$00

Data lo

$00

Data lo

$00

CRC

$----

CRC

$----

5.3.1.3 [08 02] Return Diagnostic Register

The contents of the slave‘s 16 bit diagnostic register are returned in the response. The assignment of

diagnostic register bits in Protocol

Plus controllers is shown below. In the register, bit 15 is the high-

order bit. The description is TRUE when the corresponding bit is set to logic 1.