ProSoft Technology MVI56-AFC - Manual (Page 168)

MVI56-AFC Backplane Communication MVI56-AFC ♦ ControlLogix Platform
User Manual Liquid and Gas Flow Computer
Page 168 of 316 ProSoft Technology, Inc.
February 25, 2011
11.2.1 Function Block Structure
The first word of each output and input function block, called the "block ID",
specifies the block type, control flags, addressing, and additional information
depending on type. For each function block type, the matching input function
block (returned by the AFC) also contains a block ID. Portions of this word echo
the output verbatim, while the remainder may contain status information about
the result of the action.
Each output function block ID is verified by the AFC to be unambiguous; any
value that is out of range, or any undefined bit that is set to 1, causes a format
alarm.
The typical structure of a function block is shown in the following diagram:
Typical Output Function Block (OFB)
Element Attribute
0 Block ID: Function Code, Processing Controls, Length or Meter/Stream
Selection
1 Data Block Length
2
. . .
. . .
N
Typical Input Function Block (IFB)
Element Attribute
0 Block ID: Function Code Echo, Status and Alarms, Meter and Active Stream Numbers
1 Data Block Length
2
. . .
. . .
N