Specifications

Hardware Configuration
2–31
2.10.6 Using SRAMs
If you install an SRAM in socket S0, you can provide backup power from an external battery connected
to J16 when power is off by shorting W2 and W21-2/3.
The external battery power is connected to the SRAM through a low forward voltage drop Schottky diode
and a solid state switch that senses the state of Vcc (+5V).
Note
Some byte-wide devices draw battery backup current through their
chip select lines when power is off. When using memory devices
that do not require battery backup, remove the jumper on W2 and
set W21 to 1/2. This prevents the backup battery from being
drained prematurely.
Table 2–23 SRAM and NOVRAM Jumpering for S0
SRAM
Typical Devices Pins Jumper Diagram
32K SRAM 43256
128K SRAM 628128
32K NOVRAM Dallas DS1235Y
Benchmarq BQ4013Y
28
32
512K SRAM 628512
512K NOVRAM Dallas DS1650Y
Benchmarq BQ4015Y
32
NOTE: W2 and W21 are shown configured to provide backup power to the SRAM to
make it into a non-volatile RAM (NOVRAM). To configure W2 and W21 for a
NOVRAM (a device that already has an internal battery), remove the jumper from W2
and move the jumper on W21 to 1/2.
2.10.7 Byte-Wide Socket Signals
Jumper arrays W15, W2, and W21 configure the byte-wide socket for specific memory devices. The
figures in the previous sections show how to set the jumpers for familiar devices. The following table
lists the signals that appear on the pins of W15. Use this table if you need to configure the socket for a
device not shown in the configuration figures.