USPIIe-USB Hardware Manual
1-14
Themis Computer
1.6
TOD/NVRAM Battery Replacement
The Non-Volatile RAM (NVRAM) and a Time-of-Day (TOD) clock are both con-
tained in the timekeeper chip (see Chapter 3, "Hardware Overview"). The chip has
its own lithium battery to operate the TOD clock and maintain the contents of the
NVRAM during a power shutdown. Located directly on top of the timekeeper chip,
the battery provides power backup for approximately 10 years.
In the event the battery must be replaced, follow these steps:
1.
Locate the lithium battery on the top (component) side of the USPII
e
-USB
board (see
Figure 1-4
).
2.
Remove the phillips-head screw securing the battery holder to the board (see
A
and
B
in
Figure 1-5
on page 1-15).
Figure 1-4.
Location of the TOD/NVRAM Battery
4-pin, keyed
Lithium Battery
TOD/NVRAM
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