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OPERATIONS MANUAL PPM-LX800-G
33
CMOS Storage Location
The PPM-LX800-G’s BIOS configuration is stored in three (3) locations:
(1) CMOS RAM (nonvolatile if battery backed)
(2) EEPROM (nonvolatile storage for user defaults)
(3) FLASH PROM (nonvolatile storage for factory defaults)
BIOS Settings Storage Options
At system boot, the BIOS first performs a checksum validation on the contents of the
CMOS RAM. Invalid checksums usually occur due to a low or disabled battery. If the
checksum is valid, the system boots using values stored in CMOS RAM. If a checksum
error occurs, the BIOS attempts to load CMOS values from the EEPROM.
After a checksum validation, the BIOS configuration is loaded from the EEPROM and
the boot process continues. If the EEPROM is disabled or the contents of the EEPROM
fail the checksum validation, the system loads the factory default settings from the
FLASH PROM and continues the boot sequence.
For applications where the battery is present, CMOS settings should be saved to
both the CMOS RAM and to the EEPROM. If the battery fails, the CMOS defaults will
be loaded from the EEPROM so the system can continue to function without user
interaction and only time and date information will be lost.
7 5 3 1
o o o o
o o o o
8 6 4 2
J1
Saving the CMOS Configuration
The Real-Time Clock and the CMOS RAM settings can be maintained by an optional
battery when the board is powered off. The battery can be enabled/disabled with
jumper pins 5 and 6 at
J1
. A battery is always required to maintain time and date
functions when the board is powered off.
The EEPROM feature allows the user to save CMOS configuration settings to nonvolatile
storage that does not require a battery. This feature can be enabled/disabled using
pins 3 and 4 of
J1
. When enabled, the user’s CMOS settings can be saved to EEPROM
from the BIOS utility’s Main Menu. If the board is powered off with no battery, the
user’s CMOS settings will be restored from EEPROM but time and date information will
be lost and returned to default values.
Enables EEPROM BIOS Settings (default)
3-4
Disables EEPROM BIOS Settings
3 4
Enables Battery (default)
5-6
Disables Battery
5 6
