ProSoft Technology MVI56-AFC - Manual (Page 196)

MVI56-AFC Backplane Communication MVI56-AFC ♦ ControlLogix Platform
User Manual Liquid and Gas Flow Computer
Page 196 of 316 ProSoft Technology, Inc.
February 25, 2011
Special Notes
If Bit 0 (F) of the Block ID element of the input Function Block is set:
o
Indicates Modbus exception: Illegal function (requested number of
registers is 0).
If Bit 1 (A) of the Block ID element of the Input Function Block is set:
o
Indicates Modbus exception: Illegal address (an attempt to access one or
more non-existent Modbus registers).
If Bit 2 (V) of the Block ID element of the Input Function Block is set:
o
Indicates Modbus exception: Illegal data value (never occurs for a "read"
function).
Note: If any of the above three bits are set, it indicates that no action on the OFB has been taken
by the AFC module.
Note: Refer to Function Block Structure (page 168) for information on Bit 8 and 9 settings.
11.2.12 Function Block Definition - 20, 21: Modbus Gateway Write
Output Function Block ID
Function Code 20: Write to Modbus Registers in the PRIMARY Slave HOLDING
register bank.
Function Code 21: Write to Modbus Registers in the VIRTUAL Slave HOLDING
register bank.