ProSoft Technology MVI56-AFC - Manual (Page 199)

MVI56-AFC ♦ ControlLogix Platform MVI56-AFC Backplane Communication
Liquid and Gas Flow Computer User Manual
ProSoft Technology, Inc. Page 199 of 316
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 (either the requested number
of registers is 0 or all the registers addressed are read-only).

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 (an attempt to write a value
to a register that is out of range or otherwise invalid for its intended target
OR an attempt to change a sealable parameter while the Event Log is
full).
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.
11.2.13 Function Block Definition - 24, 25, 26: Modbus Master
Output Function Block ID
Function Code 24: Modbus Master READ from slave’s HOLDING register or
COIL bank
Function Code 25: Modbus Master READ from slave’s INPUT register or INPUT
status bank