Rockwell Automation 1747-SDN SLC 500 DeviceNet Scanner Module User Manual - Manual (Page 127)

Publication 1747-UM655B-EN-P - June 2007
Configuring the M0/M1 Files by Using RSLogix 500 Software 127
The first two ladder diagrams in the last section illustrate a technique
you use to capture and use M0 or M1 data as it exists at a specific
time. In the first diagram, bit M1:2.1/1 could change state between
rungs 1 and 2. This could interfere with the logic applied in rung 2.
The second diagram avoids the problem. If rung 1 is true, bit B3/10
captures this information and places it in rung 2.
The following diagram illustrates another economizing technique. The
COP instruction addresses an M1 file, adding approximately 4.29 ms
to the scan time if you are using an SLC 5/02, series B processor. You
can save scan time by making this rung true periodically only. For
example, you can use a clock bit S:4/8 (clock bits are discussed in the
programming manual).
A rung such as this might be used when you want to monitor the
contents of the M1 file, but monitoring need not be continuous.
In this example, a COP instruction can be used to monitor the
contents of an M1 file. When the instruction goes true, the six words
of data in file #M1:4.3 is captured as it exists at that time and placed in
file #N10:0. All subsequent logic should address the data in #N10:0.
The data will be consistent and it shortens scan time by eliminating
reads to the module each time an M0 or M1 address is encountered in
the program.
[OSR]
B11
0
COP
COPY FILE
Source
Dest
Length
] [
S:4
8 #M1:4.3
#N10:0
6
S:4/8 causes the M1:4.3
file to update the N10:0 file
every 2.56 seconds.