Rockwell Automation 1775-MX_S4A,D17756.3.1 User Manual PLC-3 BACKUP CONC(OR.DU1 - Manual (Page 118)

Diagnosing Faults
Chapter 6
6-14
Table 6.J
Results
If the Processor Detects: The 1775 - GA or 1775 - S4B
Procedure Will Display:
No fault NO FAULT DETECTED
A fault in the main program section <major fault> DETECTED AT RUNG
RM<number>
A fault in the subroutine program <major fault> DETECTED AT RUNG RS
<number>
A fault in the fault routine program <major fault> DETECTED AT RUNG
RF<number>
A fault that does not generate a rung
reference
<major fault>