ProSoft Technology MVI69E-MBTCP - Manual (Page 120)

Reference MVI69E-MBTCP ♦ CompactLogix Platform
User Manual Modbus TCP/IP Enhanced Communication Module
Page 120 of 150 ProSoft Technology, Inc.
May 20, 2015
Coils that are not programmed in the controller logic program are not
automatically cleared upon power up. Thus, if such a coil is set ON by function
code 15 and (even months later) an output is connected to that coil, the output is
hot.
7.2.12 Preset Multiple Registers (Function Code 16)
Query
This Function Code allows you to modify the contents of a Modbus 4x range in
the slave. This writes up to 125 registers at time. Since the controller is actively
scanning, it also can alter the content of any holding register at any time.
Note: Function codes 5, 6, 15, and 16 are the only messages that are recognized as valid for
broadcast.
The example below is a request to write 2 registers starting at register 40002 in
slave 11.
Note: This is the structure of the message being sent out to the Modbus network. The byte values
below are in hexadecimal display.
Node
Address Function
Code
Data Start
Address
High
Data Start
Address
Low
Number
of Points
High
Number
of Points
Low
Byte
Count Data
High Data
Low Data
High Data
Low Error
Check
Field (2
bytes)
0B 10 00 01 00 02 04 00 0A 01 02 CRC
Response
The normal response to a function 16 query is to echo the address, function
code, starting address and number of registers to be loaded.
Node
Address Function
Code
Data Start
Address
High
Data Start
Address
Low
Number
of Points
High
Number
of Points
Low
Error Check
Field (2 bytes)
0B 10 00 01 00 02 CRC