ProSoft Technology MVI56-AFC - Manual (Page 166)

MVI56-AFC Backplane Communication MVI56-AFC ♦ ControlLogix Platform
User Manual Liquid and Gas Flow Computer
Page 166 of 316 ProSoft Technology, Inc.
February 25, 2011
The controller may then verify the validity of the returned data by checking that
the received sentinel echo is the same as the anchor echo. If more than one
OBA is being processed, the transaction number must be used to match the IBA
(AFC output) with the originating OBA (AFC input, controller output).
Input Block Length and Format Alarm
The "length" element returned by the module in the IBA has the high-order (sign)
bit set if any formatting error is detected in the data portion of the OBA you
formatted in the logic. This is referred to as a "format alarm". The remainder of
the input length element contains the number of data words successfully
processed before any formatting inconsistencies were detected by the AFC
module and the alarm condition annunciated. If no formatting error exists, the
length element will echo the output length you entered. If the output length
element itself raises an alarm (for example, value > 245), then the returned
length value is -1.