Allen-Bradley 1747-SN - Appendix B M0-M1 Files and G Files; M0-M1 Files

Appendix B
Publication 17476.6 - July 1996
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 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 appendix D of the
SLC 500t and MicroLogixt 1000 Instruction Set
Reference Manual, Publication 1747-6.15.
Configuring M0-M1 Files Using APS Software
M0 and M1 files are configured as part of the I/O configuration
procedure for the processor file. After you have assigned the
specialty I/O module to a slot (the procedure is the same as assigning
other modules), the following functions appear at the bottom of the
APS screen:
F4 F5 F6 F7
MODIFY
RACKS
MODIFY
SLOT
DELETE
SLOT
UNDEL
SLOT
F8 F9
EXIT SPIO
CONFIG
F1 F2
READ
CONFIG
ONLINE
CONFIG
M0-M1 Files