Rockwell Automation 1747-BSN Backup Scanner Module - Manual (Page 143)

1 Publication 1747-UM010B-EN-P - September 2003
Chapter
9
Programming Techniques
Chapter Objectives Read this chapter to familiarize yourself with techniques used to
program your SLC 500 backup system.
In this chapter we describe:
•
how to get started with a program to transfer data table values
•
two methods you can use to program the SLC 500 backup
system to transfer data table values
•
the behavior of specific instructions when used in your
application program, and give you suggestions for dealing with
these instructions.
Getting Started The 1747-BSN modules control switchover and transfer remote I/O
data without additional programming. However, if you want to
transfer data table values from the primary to the secondary processor,
you must provide a ladder program. The following figure shows the
minimum ladder programming you must provide to transfer 2 Kwords
of the data table between the two 1747-BSN modules, and to provide
1747-BSN module status. This program constantly transfers data as fast
as possible. 2K words is the maximum per 1747-BSN module on the
HSSL. With no local I/O, an SLC 5/02 or later processor supports up to
8 1747-BSN modules for a maximum of 16K words of retentive data
transfer from primary processor to secondary processor. Refer to the
following section, Data Transfer Schemes, for alternative approaches.
You need to put this program in both processors.