ProSoft Technology MVI56-AFC - Manual (Page 198)

MVI56-AFC Backplane Communication MVI56-AFC ♦ ControlLogix Platform
User Manual Liquid and Gas Flow Computer
Page 198 of 316 ProSoft Technology, Inc.
February 25, 2011
Description
These two function codes allow you to write data from the controller to the vast
address space of the AFC module for its consumption. The two functions are
designed to access the two separate holding register banks by assigning unique
function codes for each type of access. These two function codes are tabulated
below in this section.
This block performs an arbitrary data transfer between the PLC and the AFC
data table. Any data transfer that can be performed with a Modbus command to
either AFC slave through any of the module’s ports may be implemented using
the gateway.
Any data words not relevant to the command are ignored upon output (to the
AFC) and zero upon input (from the AFC). Gateway data transfer may be
controlled through the use of the "ignore output" bit of the block ID. The "skip
input" bit has no function and is ignored.
MB Gateway Write: OFB MB Gateway Write: IFB
Element Attribute Element Attribute
0 Block ID - Function Code &
Length
0 Block ID - Function Code &
Status
1 Modbus Register Address 1 Reserved
2 Write Number of Registers (m) 2 Reserved
3 Data (write) Element 1 3 Reserved
4 Data (write) Element 2 4 Reserved
5 Data (write) Element 3 5 Reserved
… ……………………….. … Reserved
… ……………………….. … Reserved
n Data (write) Element (n-2) n Reserved
Note: The number of registers for a Gateway Write Function block must not exceed two less than
the data block length declared in the OFB ID.
Modbus Gateway Write Function Codes
Function Code To Write to Register Bank To address AFC Slave
20 Holding Primary
21 Holding Virtual