11
MAINTENANCE AND INSPECTION
11.3 Battery Life and Replacement Procedure
11 - 5
9
EMC AND LOW
VOLTAGE
DIRECTIVES
10
LOADING AND
INSTALLATION
11
MAINTENANCE AND
INSPECTION
12
TROUBLESHOOTING APPENDICES INDEX
11.3 Battery Life and Replacement Procedure
The batteries installed in the CPU module and SRAM card are used for data retention of
the program memory, standard RAM, and latch device during the power failure. Special
relays SM51 and SM52 turn on due to the decrease of battery voltage. Even if the special
relays turn on, the program and retained data are not erased immediately.
After relay SM51 turns on, replace the battery quickly within the data retention time for
power failure (3 minutes).
POINT
SM51 turns on when the battery voltage falls below the specified value, and
remains ON even after the voltage is recovered to the normal value.
SM52 turns on when the battery voltage falls below the specified value, and turns
OFF when the voltage is recovered to the normal value.
After SM51 and/or SM52 turns on, replace the battery quickly.
SM51 and SM52 turn on when the battery voltage of the CPU module or SRAM card is
lowered.
To identify the specific battery of the memory of which voltage is lowered, check the
contents of the special resisters SD51 and SD52.
For details of SD51 and SD52, refer to Section 12.8.
POINT
The cases for memory retention by the CPU module battery and the SRAM card
battery are described below.
The important points are:
1) The CPU module battery cannot retain the SRAM card memory.
2) The SRAM card battery cannot retain the CPU module memory.
: Retained, : Not retained
Diagram 11.1 Bit pattern
Table11.3 Cases for memory retention by the CPU module battery and the SRAM card battery.
Power supply
Module
Battery of CPU
Module
SRAM card
battery
Memory of CPU
Module
Memory of SRAM
Card
ON
Connected
Installed
Not installed
Not connected
Installed
Not installed
OFF
Connected
Installed
Not installed
Not connected
Installed
Not installed
b3to b4 b2 b1 b0
b15
SD51, SD52
Fixed at 0
Battery error for CPU module
Battery alarm for SRAM card
Battery error for SRAM card
When the battery
voltage is low, the
value is "1."
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