80 Rockwell Automation Publication 1756-UM058G-EN-P - November 2012
Chapter 4 Diagnostic Module Features
Fault bits in the field-power loss word and open wire word are logically entered
into the module-fault word. Depending on the module type, a bit set in the
module-fault word can mean multiple things, as indicated in the table.
The following illustration provides an overview of the fault reporting process for
digital input modules.
Table 13 - Bits Set in Module-fault Word
Condition Bits Set
Communications fault All 32 bits are set to 1, regardless of the module’s density.
Field-power loss
Only the bit affected is set to 1.
Open wire
Module-fault Word
All modules
Field Power Loss Word
1756-IA8D only
Open Wire Word
Bit 31 Bit 0
An open wire condition on any point sets the bit for that point in the open
wire word and also sets the appropriate bit in the module-fault word.
A loss of field power sets the bit for that group in the field-power loss
word and also sets the appropriate bit in the module-fault word.
A communications fault sets all bits in the module-fault word. A field-power loss
or open wire condition sets the appropriate bit in the module -fault word.
1
1
1
1
Group 0
Group 1
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