Rockwell Automation Allen-Bradley ControlLogix 1756-MVI Programming Reference Manual page 26

3-4 MVI Backplane API
Publication 1756-RM004B-EN-P - October 2000
The status connection may be used by the processor to determine the
current status of the 1756-MVI module. The first word of the status
input data contains the status bits shown in table 3.C.
Bit Description
0 Module is ready (MVI driver is loaded)
1 Module application is active (MVIbp_Open has been called)
15 Module is faulted (MVIbp_SetModuleStatus called with MVI_MODULE_STATUS_FAULTED
The remaining two words of status data are simple counters which are
incremented by the module whenever a message is sent via
MVIbp_SendMessage (word 1) or received via MVIbp_ReceiveMessage
(word 2). These counters may be used for synchronization or diagnostic
purposes.
Table 3.C - Status Input Word 0