2.7
Battery Installation/Replacement
The on-board Real-Time Clock and CMOS memory used by the PC BIOS firmware are powered
by a 3.3V Lithium battery when the board is powered OFF. This battery also powers the static
RAM device. It is advisable, though not essential, for the battery to be fitted prior to using the
board. Figure 2-9 shows how to do this. One battery is supplied with the board, but it is not
normally fitted.
If the board is operated without a battery, the User Selectable NVRAM Defaults feature can be
used to override the factory default NVRAM settings. See Section 10.6 for further details.
The battery should be replaced when the voltage falls below 2.8V. Depending on the way in
which the board is operated and stored, battery life should be in excess of 5 years. The life
expectancy will fall if the battery is subjected to long periods at temperatures of 45
o
C or above.
It will also fall if the battery is fitted to a board that is stored in it’s conductive bag even at room
temperature.
CAUTION
When replacing the battery, proper anti-static precautions must be observed.
WARNING
Dispose of battery properly. DO NOT BURN. The date and time settings will need
to be initialized if the battery is disconnected.
If the BIOS setup screens have been used to set up the board for an invalid configuration, or in
other fault conditions, it may be useful to be able to reset the contents of the CMOS RAM and
Real-Time Clock. In this case, the CMOS Clear Jumper can be used.
To clear the CMOS RAM to a known state, fit the CMOS Clear jumper and apply power. When
the board is next powered down remove the jumper, otherwise CMOS RAM will again be reset.
PP 110/01x
2-11
Hardware Installation
+
BR2032
Top is marked positive
Bottom is negative
snap in /
lever out
CMOS Clear
Normal
Clear
Figure 2-9 Battery Fitting and CMOS Clear Jumper
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