Method and circuit for safeguarding CMOS RAM data in a computer system at low battery power

• US 6,266,786 B1
• Filed: 11/25/1998
• Issued: 07/24/2001
• Est. Priority Date: 08/04/1998
• Status: Expired due to Term

• Current Assignee: VIA Technologies Incorporated (VIA Technologies)
• Original Assignee: VIA Technologies Incorporated (VIA Technologies)
• Inventors: Chang, Nai-Shung
• Primary Examiner(s): Beausoleil, Robert
• Assistant Examiner(s): BADERMAN, SCOTT T
• Application Number:
  US09/199,845
• Time in Patent Office: 972 Days
• Field of Search: 714/14, 714/22, 714/24, 713/320, 713/323, 713/324, 713/340, 713/330
• US Class Current: 714/22
• CPC Class Codes: G06F 1/305 in the event of power-supply fluctuations

Abstract

A method and circuit is provided for safeguarding the data stored in a CMOS RAM (Complementary Metal-Oxide Semiconductor Random Access Memory) unit in a computer system, such as an IBM-compatible personal computer (PC), when the battery unit used to power the CMOS RAM unit is below working level. By this method and circuit, when the PC is powered off, the current power level of the battery unit is detected to see whether it is below working level; if yes, the main power of the PC is turned on; then the data currently stored in the CMOS RAM unit are moved to a backup-data storage unit such as the hard disk; and after this, the main power is turned off again. At the next time the PC is powered on, the data currently stored in the backup-data storage unit are moved back to the CMOS RAM unit; and after this, a message is displaying on the monitor screen requesting the user to replace the CMOS RAM battery with a new one.

Claims

1. A method for use on a computer system with a CMOS RAM unit powered by a battery unit to safeguard the CMOS RAM data when the battery power from the battery unit is below working level, comprising the steps of:

(1) in power-off state, detecting whether the current power level of the battery unit is below working level;

if yes, performing the substeps of;

(1-1) turning on the main power of the computer system;

(1-2) moving the data currently stored in the CMOS RAM unit to a backup-data storage unit; and

(1-3) turning off the main power of the computer system;

(2) at the next time the computer system is powered on, moving the data currently stored in the backup-data storage unit back to the CMOS RAM unit; and

(3) displaying a message requesting the user to replace the battery unit with a new one.

2. The method of claim 1, wherein the backup-data storage unit is a hard disk.

3. A CMOS RAM data safeguarding circuit for use on a computer system of the type having a power supply capable of generating a main power and a standby power and having a CMOS RAM unit powered by a battery unit when the computer system is powered off and by the main power from the power supply when the computer system is powered on, for safeguarding the data stored in the CMOS RAM unit when the power from the battery unit is below working level;

the CMOS RAM data safeguarding circuit comprising;

a backup-data storage unit;

a battery power detector, which is powered by the standby power from the power supply when the computer system is powered off, for detecting whether the battery power from the battery unit is below working level;

if yes, the battery power detector generating a backup request signal; and

a main control unit, which is powered by the main power from the power supply when the computer system is powered on and by the standby power from the same power supply when the computer system is powered off;

capable of, when activated by the backup request signal from the battery power detector, moving the data currently stored in the CMOS RAM unit to the backup-data storage unit, and thereafter, at the next time the computer system is powered on, moving the backup data from the backup-data storage unit back to the CMOS RAM unit.

4. The circuit of claim 3, wherein the backup-data storage unit is a hard disk.

5. The circuit of claim 3, wherein the power supply is of the type capable of being switched on and off automatically through software means.

6. A CMOS RAM data safeguarding circuit for use on a computer system of the type having a power supply capable of generating a main power and a standby power and a CMOS RAM unit powered by a battery unit when the computer system is powered off and by the main power from the power supply when the computer system is powered on, for safeguarding the data stored in the CMOS RAM unit when the power from the battery unit is below working level;

the CMOS RAM data safeguarding circuit comprising;

a battery power detector, which is powered by the standby power from the power supply when the computer system is powered off, for detecting whether the battery power from the battery unit is below working level;

if yes, the battery power detector generating a backup request signal; and

a main control unit, which is powered by the main power from the power supply when the computer system is powered on and by the standby power from the same power supply when the computer system is powered off, capable of, when activated by the backup request signal from the battery power detector, moving the data currently stored in the CMOS RAM unit to a permanent data storage unit of the computer system, and thereafter, at the next time the computer system is powered on, moving the backup data from the data storage unit back to the CMOS RAM unit.

7. The circuit of claim 6, wherein the data storage unit is a hard disk.

8. The circuit of claim 6, wherein the power supply is of the type capable of being switched on and off automatically through software means.