GE 90-30 PLC Series Installation And Hardware Manual page 156

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In the rung shown above, the %SA011 contact will close when a low battery is detected by the
PLC. This will turn on the %Q output coil, which addresses an output module's output that will
turn on a warning light. An alternate method would be to communicate the status of the coil
(which, in that case, would probably be a %M coil) to a Human to Machine Interface (HMI)
terminal such as a GE CIMPLICITY HMI unit. The HMI could be programmed to display a
warning message when that particular bit goes to a logic 1. For more information about System
Reference bits and ladder logic programming, see the Series 90-30/20/Micro PLC CPU Instruction
Set Reference Manual, GFK-0467.
GFK-0356Q Chapter 6 Memory Backup/Battery Backup 6-5