CPUs, Memory Cards, Memory Submodules, Interface Submodules

5.10.3RAM Submodules with Battery Backup

 

RAM submodules with battery backup are used when the contents of the

 

memory submodules must be retained even outside the CPU. You can then

 

remove the battery-backed 377 memory submodule from the CPU without

 

loss of data. An integral battery protects the submodule from data loss, and

 

ensures that the data will be retained until the RAM submodule is used again.

 

 

 

Note

 

The RAM submodule with battery backup is not a substitute for an EPROM

 

submodule. The contents can be overwritten by a STEP 5 program. The

 

battery can discharge if the submodule is at standby for a long time. This can

 

result in the loss of data.

 

 

 

To protect the battery, the 377 memory submodule has a cover on both sides.

 

The button cell battery with terminal lugs is secured on the submodule with

 

screws on two holders. When the grip is swivelled in, you can see the battery

 

fault LED.

Operational States

There are three different operational states for the RAM submodule with

 

battery backup:

Normal Operation

In this state

 

S the battery-backed RAM submodule is in the CPU;

 

S the programmable controller (PLC) is switched on (Power On);

 

S and neither the backup battery of the PLC nor the battery of the RAM

 

submodule is supplying power.

 

 

 

Note

 

The RAM submodule must not be inserted or removed during the RUN state;

 

this can result in data corruption, loss of data or CPU malfunctions.

 

 

System Manual

5-85

C79000-G8576-C199-06

Page 224 Page 226
Page 225
Image 225
Siemens S5-135U/155U appendix RAM Submodules with Battery Backup, Operational States, Normal Operation
Page 224 Page 226
Top Page Image Contents