Preset single register (function code 06) – ProSoft Technology MVI69E-MBS User Manual
Page 120
Reference
MVI69E-MBS ♦ CompactLogix Platform
User Manual
Communication Module
Page 120 of 162
ProSoft Technology, Inc.
January 6, 2014
Node
Address
Function
Code
Data Coil Point
High
Data Coil Point
Low
Data On/
Off
Data Error Check
Field (2 bytes)
0B
05
00
AC
FF
00
CRC
The forcing of a coil via Modbus function 5 happens regardless of whether the
addressed coil is disabled or not (In ProSoft products, the coil is only affected if
you implement the necessary ladder logic).
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 is "hot".
7.2.7 Preset Single Register (Function Code 06)
Query
This Function Code allows you to modify the contents of a Modbus 4x range in
the slave. This writes to a single register only. Any holding register that exists
within the controller can have its contents changed by this message. However,
because the controller is actively scanning, it also can alter the content of any
holding register at any time. The values are provided in binary up to the
maximum capacity of the controller. Unused high order bits must be set to zero.
When used with Slave address zero (Broadcast mode) all Slave controllers load
the specified register with the contents specified.
Note Functions 5, 6, 15, and 16 are the only messages that are recognized as valid for broadcast.
The exa
mple below is a request to write the value ‘3’ to register 40002 in slave
11.
Node
Address
Function
Code
Data Start
Point High
Data Start
Point Low
Preset Data
Register
High
Preset Data
Register
Low
Error Check
Field (2 bytes)
0B
06
00
01
00
03
CRC