Battery Replacement - Mitsubishi Electric MELCEC Q Series User Manual

7. MEMORY CARD AND BATTERY
7.7

Battery Replacement

Special relay M9006 or M9007 turns on when voltage of the battery for backing up
programs and power failure compensation function drops. The program and power failure
compensation data are not erased immediately when any of these special relays turns on,
while these data may be erased if the on status of the special relay fails to be recognized.
Replace the battery before the total of power failure compensation time after M9006 or
M9007 turns on reaches the specified time.
M9048 turns on at a voltage drop of the battery for a SRAM card.
The reference battery life and replacement procedures are described on the following
pages.
POINT
M9006 is a battery voltage drop alarm and the data are retained within the
specified time after M9006 turns on; however, the battery should be replaced as
immediately as possible.
POINT
The relationship of backup between the status of the batteries installed in CPU
modules and SRAM cards is explained below.
The following two points are applied.
1) The battery in the CPU module does not back up the memory of the SRAM card.
2) The battery in the SRAM card does not back up the memory of the CPU module.
AC power
Battery in CPU
supply to CPU
module
ON
OFF
Battery in
module SRAM card
ON
ON
OFF
ON
OFF
OFF
ON
ON
OFF
ON
OFF
OFF
: Backup is possible.
7 - 8
Memory of Memory of
CPU module SRAM card
: Backup is not possible.