Rockwell Automation 1747-BSN Backup Scanner Module - Manual (Page 181)

1 Publication 1747-UM010B-EN-P - September 2003
Appendix
B
M0-M1 Files and G Files
This appendix contains important information about M0-M1 files and
G files. The information is general in nature and supplements specific
information contained in earlier chapters of this manual. Topics
include:
•
M0-M1 Files
•
G Files
M0 and M1 files are data files that reside in specialty I/O modules
only. There is no image for these files in the processor memory. The
application of these files depends on the function of the particular
specialty I/O module. With respect to the SLC processor (SLC 5/02 or
later), the M0 file is a module output file (a write only file) and the M1
file is a module input file (a read only file). The opposite is true for
specialty I/O modules, where the M0 file is a read only file, and the
M1 file is a write only file.
M0-M1 Files M0 and M1 files can be addressed in your ladder program and they
can also be acted upon by the specialty I/O module - independent of
the processor scan. It is important that you keep the following in
mind in creating and applying your ladder logic:
IMPORTANT
During the processor scan, the ladder program can
address M0 and M1 data with bit, word, or file
instructions. Each time an M0-M1 file address is
encountered in the program, an immediate data
transfer to or from the specialty I/O module occurs.
The impact these immediate data transfers have on
processor scan time is described in the SLC 500
Instruction Set Reference Manual, Publication
1747-RM001.