Electrical computers and digital processing systems: support – Computer power control
Reexamination Certificate
1993-08-09
2001-05-08
Wiley, David A. (Department: 2155)
Electrical computers and digital processing systems: support
Computer power control
C713S152000
Reexamination Certificate
active
06230273
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to computers and circuits for turning computers on and off, and more specifically to a hardware and software controlled on/off circuit for computers.
Security of computers, especially retail point-of-service (POS) terminals is of utmost importance to the end user of the product. To that end, it would be highly undesirable to a retailer if power to the terminal were accidentally (or intentionally) removed. A complete shutdown of the terminal would result in a loss of transaction data. The terminal would have to be re-booted and the entire program contents of the terminal would have to be reloaded, jobs which necessarily consume a great deal of time.
Therefore, it would be desirable to provide a hardware and software controlled on/off circuit for a computer requiring security, such as a retail terminal. It would also be desirable for the on/off circuit to provide “fail-safe” hardware control over power removal, while providing a topology wherein the resident terminal software plays an intervening role in the power removal process.
SUMMARY OF THE INVENTION
In accordance with the teachings of the present invention, a hardware and software controlled on/off circuit for computers is provided. The on/off circuit comprises a control circuit which produces first and second signals, wherein the first signal causes the computer to execute a software program which prepares the computer for power removal and which returns a third signal to the circuit when the software program has prepared the computer for power removal, and wherein the circuit produces the second signal to disconnect the power supply in response to the third signal.
If for some reason the software program should “lock-up” the computer, the on/off circuit and provides the second signal to disconnect the power supply if the software program has not sent the third signal after a predetermined time from when the control circuit sent the first signal to the software program so that the computer may be shut down.
The on/off circuit also includes a power switch having on and off positions, and a key switch having authorized and unauthorized positions, wherein both switches provide input signals to the control circuit. The control circuit produces the first signal only if the power switch is in the off position and the key switch is in the authorized position.
The power supply preferably includes a logic on/off power supply and the control circuit includes a one-shot multivibrator coupled to the computer, the power switch, and the key switch. The key switch produces a reset signal for resetting the one-shot multivibrator when the key switch is in the unauthorized position. The one-shot multivibrator produces the first signal in response to the off signal from the power switch when the key switch is in the authorized position. The control circuit also includes a logic off command circuit coupled to the computer which produces the second signal, which is a logic off command signal.
The fail-safe feature of the control circuit is provided by a timer and an additional one-shot multivibrator. The timer circuit is coupled to the first one-shot multivibrator and times a predetermined time period from receipt of the first signal to allow the software program to disconnect the power supply. If the software program is malfunctioning, the additional one-shot multivibrator produces a safety signal which signals the logic off command circuit to disconnect the power supply, thus allowing the computer to be shut down.
It is accordingly an object of the present invention to provide a hardware and software controlled on/off circuit for computers.
It is another object of the present invention to provide a hardware and software controlled on/off circuit for computers which has a hardware fail-safe circuit for allowing the computer to be shut down if the software fails.
REFERENCES:
patent: 4312035 (1982-01-01), Greene
patent: 4635195 (1987-01-01), Jeppesen, III et al.
patent: 4654821 (1987-03-01), Lapp
patent: 4668878 (1987-05-01), Wyss
patent: 4791453 (1988-12-01), Koseki et al.
patent: 4868832 (1989-09-01), Mavington et al.
patent: 5339446 (1994-08-01), Yamasaki et al.
Martin Paul W.
NCR Corporation
Wiley David A.
LandOfFree
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