Rockwell Automation Allen-Bradley 5069-L3100ERMS2, User Manual

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140 Rockwell Automation Publication 5069-UM003B-EN-P - January 2020
Appendix B Modbus Command Codes
Preset Multiple Registers (Function Code 16)
Query
The Function Code allows you to modify the contents of a Modbus 4x range in
the slave. This writes up to 125 registers at a time. Since the controller is actively
scanning, it can alter the content of any holding register at any time.
The following example is a request to write two registers starting at register
40002 in slave 11.
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.
TIP Functions 5, 6, 15, and 16 are the only messages that are recognized as valid
for broadcast.
TIP This is the structure of the message being sent out to the Modbus network.
The following byte values 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 High
Data Low
Data High
Data Low
Data Error Check
Field
(2 bytes)
0B 10 00 01 00 02 04 00 0A 01 02 CRC
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