Televisions do not typically remember the last operating state of the set in the event of a power failure. Thus, the occurrence of a power failure may necessitate reprogramming of the set to restore it to the same state it had at the time of the power outage. One piece of data which may not be stored is the time of day, which is typically counted by a clock. In order to save money, the clock does not have its own power source, and so the clock loses the current time upon power failure. There are other pieces of data which might be useful in restoring the state of a television receiver after a power failure, such as the ON or OFF state of the set, the audio volume level and the channel.
In one prior-art scheme, an Eeprom was used to store data from a microprocessor of the receiver during a power failure. The video processor and Eeprom were powered until the transfer of the data to non-volatile storage occurred. As the processing power of the video processors increases for providing high definition television, so does the cost of powering the various elements required to transfer data to non-volatile storage.
Improved data storage arrangements are desired.
An Electrically Erasable Programmable Read-Only-Memory (Eeprom) may include a volatile input data buffer and a non-volatile data storage region. The time required for transfer of data into non-volatile portions of the Eeprom includes the sum of the time required to store the data in the buffer, plus the time required to transfer the data from the buffer to the non-volatile storage region. According to an aspect of the invention, power is applied to the processor of the system upon the occurrence of a power failure for only so long as is required in order to sense the power failure and to transfer the data to be stored from the processor to the buffer of the Eeprom. Power is provided to the relatively high-power processor for only the minimum time required for the data transfer, and the relatively low-power Eeprom can be maintained operative for an additional length of time to allow it to complete the transfer of data from the buffer to the non-volatile storage portion of the Eeprom.