ProSoft Technology MVI69L-MBTCP User Manual

Page 114

Reference

MVI69L-MBTCP ♦ CompactLogix Platform

User Manual

Communication Module

Page 114 of 152

ProSoft Technology, Inc.

January 6, 2014

The use of Server address 00 (Broadcast Mode) will force all attached Servers to
modify the desired coil.

Note: Functions 5, 6, 15, and 16 are the only messages that will be recognized as valid for

broadcast.

The example below is a request to Server number 11 to turn ON coil 0173.

Node
Address

Function
Code

Data Start
Point High

Data Start
Point Low

Number of
Points High

Number of
Points Low

Error Check
Field (2 bytes)

CRC

Response
The normal response to the Command Request is to re-transmit the message as
received after the coil state has been altered.

Node
Address

Function
Code

Data Coil Point
High

Data Coil Point
Low

Data On/
Off

Data Error Check

Field (2 bytes)

CRC

The forcing of a coil via MODBUS function 5 will be accomplished regardless of
whether the addressed coil is disabled or not (In ProSoft products, the coil is only
affected if the necessary ladder logic is implemented).

Note: The Modbus protocol does not include standard functions for testing or changing the
DISABLE state of discrete inputs or outputs. Where applicable, this may be accomplished via

device specific Program commands (In ProSoft products, this is only accomplished through ladder

logic programming).

Coils that are reprogrammed in the controller logic program are not automatically
cleared upon power up. Thus, if such a coil is set ON by function Code 5 and
(even months later), an output is connected to that coil, the output will be "hot".