ProSoft Technology MVI56-AFC - Manual (Page 200)

MVI56-AFC Backplane Communication MVI56-AFC ♦ ControlLogix Platform
User Manual Liquid and Gas Flow Computer
Page 200 of 316 ProSoft Technology, Inc.
February 25, 2011
Function Code 26: Modbus Master WRITE to slave’s HOLDING register or
COIL bank
Input Function Block ID
Function Block Name: Modbus Master
Function Block ID: 24, 25, 26
Target: Global
Data Block Length: User defined - from 6 to 130
Total Block Length: (User defined +1) Element
Description
This block performs an arbitrary data transfer between the ControlLogix and
external Modbus slaves connected to AFC Port 3, provided that port 3 is
configured as a Modbus master. Any data transfer to or from a slave’s holding
registers, input registers, output coils, or input status may be implemented using
this function; equivalent Modbus function codes are 1, 2, 3, 4, 15, and 16. In
addition, capability is provided for access to a slave’s "long remote" (32-bit)
registers where the slave implements them; in particular, Enron-style long integer
(5000 series) and floating-point (7000 series) registers are accessible. Any data
words not relevant to the command are ignored upon output (to the AFC) and
zero upon input (from the AFC). The "transaction number" is provided as a
resource to the PLC programmer in implementing multiplexing, if required; the
AFC copies it verbatim from output to input and does not use it in any other
manner.