Function Of The Back-Up Battery; Programmer Functions - Siemens SIMATIC S5-90U System Manual

S5-90U/S5-95U
4.4.2

Function of the Back-Up Battery

If the power fails or the programmable controller is switched off, the contents of the internal memory
are stored (retentive) only if a back-up battery is connected. When the programmable controller is
switched on, the following contents are available:
• Control program and data blocks (see Chapter 7)
• Retentive flags and counter values (see Chapter 2)
• ISTACK contents (see Chapter 5)
• System data (see Appendix B)
Note
• Only Insert or replace the battery while the PLC is switched on. Otherwise, an
"OVERALL RESET" is required after POWER ON.
• The S5-90U has no battery low LED.
If the S5-90U is briefly (approx. 20 ms to 10 s) in the POWER OFF state and no
battery back-up is provided, the PLC cannot recognize whether a backup battery is
available during the next restart.
Program data might be falsified in this way. You can help avoid a failure of the
battery back-up by regularly replacing the battery every year.
• A yellow LED on the operator panel of the S5-95U signals a failure of the back-up
battery.
Warning
!
Do not recharge lithium batteries. Danger of explosion! Dispose of used batteries as
classified waste.
4.5

Programmer functions

The serial interface (programmer interface) can be used for connecting
• Programmers or operator control and monitoring equipment,
• The PLC as a station on the SINEC L1 LAN (see Chapter 14).
EWA 4NEB 812 6115-02b
Start-Up and Program Tests
4-11