ProSoft Technology MVI56-AFC - Manual (Page 202)

MVI56-AFC Backplane Communication MVI56-AFC ♦ ControlLogix Platform
User Manual Liquid and Gas Flow Computer
Page 202 of 316 ProSoft Technology, Inc.
February 25, 2011
Error Codes
Code Description
=0 - No Error
>0 Modbus Exception Code or Communication Error
Modbus Exception codes are issued by the responding slave and listed in commonly
available Modbus protocol manuals; they lie between 1 and 127 and include:
1 - Illegal Function
2 - Illegal Address
3 - Illegal Data Value
Communication Errors are issued by the AFC:
500 - CTS Timeout
501 - Receive Timeout
502 - Bad Framing
503 - Buffer Overrun
504 - Bad Checksum/CRC
505 - Wrong Slave
506 - Wrong Function Code
507 - Wrong Length
<0 Configuration, Parameter, or Logic Error:
-1 - Master Port not configured
-2 - Master Port never used
-3 - Bad Slave Address
-4 - Bad Direction/ Target
-5 - Bad Datum Size / Swap Options
-6 - Bad Number of Data Items
Because the output block always contains the five words described above, the
block’s data length must be at least 5, else a format alarm is raised.
The number of data items given in the output block must be such that the implied
Modbus data fits entirely within the block as specified by its data length, else a
format alarm is raised. This means that for a Modbus read function, the number
of words occupied by the data must not exceed the block data length minus 2,
and for a Modbus write function, the number of words occupied by the data must
not exceed the block data length minus 5.