Configurable Options
BATTERY BACKUP SELECTION
A lithium battery can be loaded on the ZT 8825 PC board for use as
backup voltage for CMOS RAMs. Ziatech offers a 1 Amp-hour
battery as an option for the ZT 8825 (option 003). For maximum
battery life and data retention time, the CMOS RAMs should be low-
power types specifically designed for such applications (for example,
Hitachi 62256LP-15SL).
On-board battery backup is intended only for use with 32K, 128K, or
512K static CMOS RAMs (such as the Hitachi 62256LP-12SL). A
special Schottky diode with very low reverse leakage current (CR1)
and a 100 ohm current limiting resistor are used to prevent charging
the lithium battery.
Table 5-6 lists the jumper configurations for backup use for each
socket row. Jumpers 18, 19, 20, and 21 select the Vss source for each
row.
Table 5-6
Jumper Settings for Battery Backup.
TYPE OF
JUMPER NUMBER
BATTERY BACKUP
18
19
20
21
No battery backup
OUT
IN
OUT
IN
On-board backup: Row A
OUT
IN
IN
OUT
On-board backup: Row B
IN
OUT
OUT
IN
On-board backup: Row A,B
IN
OUT
IN
OUT
5-9
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