Rockwell Automation 1775-MX_S4A,D17756.3.1 User Manual PLC-3 BACKUP CONC(OR.DU1 - Manual (Page 94)

Programming Techniques
Chapter 5
5-13
1775ĆMX Module Communication
If the PLC-3 backup system uses memory communication modules, there
are additional bits in the data table status section (file 4, word 0) to indicate
communication status between memory communication modules. Status
information for the memory communication module resides in file 4,
words 0, 1, and 2 of the data table status section. You can monitor the
operation of a memory communication module by examining the contents
in word 0 of status file 4 (S4:0). Figure 5.5 and Table 5.B show the
meaning of each bit of this word.
Figure 5.5
Status Information for the Memory Communication Module
Transmissions occurring
Backup to primary data
xfer enabled
LIST/program control
Program compare fail
Program compare done
Program compare enabled
Data table file xfer
Continuous/single xfer
Backup in RUN mode
Backup in TEST mode
Backup in PROGRAM mode
Backup faulted
Backup outputs enabled
Backup locked
Primary locked
Communications error
17 16 15 14 13 12 11 10 07 06 05 04 03 02 01 00
Status File 4, Word 0 in the Data Table
10984ĆI
Important: Bit 17 preconditions bits 15 and 16.
1775ĆMX Module Program Compare
If an error occurred while executing a program comparison function, you
can pinpoint the rung location by examining words 1 and 2 of status file 4.
As shown in Figure 5.6, word 1 gives you the extended address of the
miscomparison. For example, if word 1 contained the hexadecimal value
0412 then the miscomparison is located in the user program section,
current operating context 1, in a subroutine. This information was obtained
as follows:
the value 4 designates the user program section of PLC-3 memory
the value 1 designates the current operating context
the value 2 designates the subroutine program section