Understanding your system chapter 1 – Rockwell Automation 1785-LTx,D17856.2.1 Classic PLC-5 Programmable Controllers Users Manual User Manual
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Understanding Your System
Chapter 1
1-7
Consider using this technique: If you are:
SFC
•
defining the order of events in a sequential process
Ladder Logic
•
more familiar with ladder logic than with programming
languages such as BASIC
•
performing diagnostics
•
programming discrete control
For detailed information about how you use ladder logic, see your
programming software documentation.
Backup System
The following diagram shows a typical PLC-5 backup system:
HSSL
1771ĆP4S
Power Supply
1785ĆBCM Module
PLCĆ5
Local I/O Chassis
Local I/O Chassis
Remote I/O Link
DH+ LInk
DH+ Link
18691
Remote I/O Chassis
Remote I/O Chassis
Remote I/O Link
Processor
1771ĆP4S
Power Supply
1785ĆBCM Module
PLCĆ5
Processor
In a PLC-5 backup system configuration, one system controls the operation
of remote I/O and DH+ communications. This system is referred to as the
“primary system.” The other system is ready to take control of the remote
I/O and DH+ communications in the event of a fault in the primary system.
This is referred to as the “secondary system.”
See chapter 2, “Choosing Hardware,” to select backup system hardware.
See the PLC-5 Backup Communication Module User Manual, publication
1785-6.5.4, for more information on configuring a PLC-5 backup system.