US 4,523,295 AGranted

Power loss compensation for programmable memory control system

AssigneeZenith Electronics Corporation

InventorThomas J. Zato

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Abstract

An arrangement for storing user programmed system timing information in a microprogrammable system in the event of a power outage. The system includes a static random access memory (RAM) for periodically storing microprocessor-generated timing information and an electrically erasable programmable ROM (EEPROM) which is coupled to the static RAM for the temporary storage of this information in the event of a power outage. Also provided in the system is a power down sensor responsive to an AC-coupled power supply for detecting power loss to the system. When the input voltage drops below a predetermined value, the contents of the static RAM are automatically transferred to the nonvolatile EEPROM. When system input power is restored, the stored contents of the nonvolatile EEPROM are automatically retransferred back to the static RAM for use by the microprocessor permitting the resumption of system operation as previously programmed on a time-shifted basis where the time shift equals the duration of the power outage. The system is particularly adapted for use with a user-programmed device, such as a television receiver or a video cassette recorder, in an environment where power outages of very short duration randomly occur. The present invention permits such a system to resume programmed system operation following resumption of power to the system without employing the combination of a battery, an oscillator, a CMOS RAM and appropriate recharging circuitry, as generally utilized in such systems.

In an arrangement for controlling a programmable device energized by an AC source, said arrangement including a DC power supply coupled to said AC source for generating a DC output voltage, clock means coupled to said AC source for generating real time data, programming means responsive to user-initiated inputs for generating program time data, a controller energized by said DC power supply and coupled to said programmable device, to said programming means for receiving said program time data therefrom and to said clock means for receiving said real time data therefrom, and wherein is stored a time-based control program for controlling said programmable device in accordance with said program time data referenced to said real time data, and a volatile memory coupled to said controller for temporarily storing said program and real time data during the execution of said time-based control program, a power loss protection system comprising:

power sense means coupled to said volatile memory and to said DC power supply, said power sense means comprising means for developing first control signal and capacitive means for developing second control signals respectively representing the present and a previous output voltage of said DC power supply and comparison means for comparing said first and second control signals for generating and providing to said volatile memory a write instruction when said first control signal drops below said second control signal and a read instruction when said first control signal rises above said second control signal;
and
a nonvolatile memory coupled to said volatile memory for receiving and storing said program and real time data when said volatile memory receives a write instruction and for transferring said program and real time data to said volatile memory when said volatile memory receives a read instruction for later recall by said controller in resuming control of said programmable device in accordance with said time-based control program following an interruption in the output of said DC power supply, wherein the operation of said programmable device is shifted in time by an interval equal to the duration of the interruption of said power supply.

Facts

Application

06/415,309Filed 7 Sep 1982

Granted

11 Jun 1985

Term ends

Not estimatedThe source records don’t support an estimate.

Classification8 codes

G11C 14/0063
In which the volatile element is a SRAM cell: and the nonvolatile element is an EEPROM element, e.g. a floating gate or MNOS transistor
G06F 1/30
Power supply means, e.g. regulation thereof: means for acting in the event of power-supply failure or interruption, e.g. power-supply fluctuations
G11B 15/026
Control of operating function, e.g. switching from recording to reproducing: by using processor, e.g. microcomputer
G11B 31/006
Arrangements for the associated working of recording or reproducing apparatus with related apparatus: with video camera or receiver

Abstract

Claims10