Method and circuit for backing up memory and calender
First Claim
1. A circuit for backing up memory and calendar, where a back-up power source for both a memory and a calendar keeps the memory stored and the calendar clocked when current supply from a main power source of a device with the memory and the calendar stops, comprising:
- a first power source circuit to supply back-up current to both the memory and the calendar; and
a second power source circuit to supply continuously back-up current to the calendar when the supply of back-up current to the memory stops due to reduction in the capacity of said first power source circuit;
said first power source circuit comprises a single sub-cell to back up both the memory and the calendar, a charging circuit to charge said sub-cell, and a memory back-up control circuit to control the back-up current of the memory; and
said second power source circuit comprises a sub-cell capacity monitoring circuit that is inserted between said sub-cell and said memory back-up control circuit, and that stops the current supply to the memory and supplies back-up current only to the calendar when detecting that the rest of capacity of said sub-cell becomes less than a predetermined value.
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Accused Products
Abstract
Disclosed is a method far backing up memory and calendar, which has the steps of: providing a back-up power source for the calendar separated from the back-up power source for both the memory and the calendar; and continuing to back up the calendar by the separated back-up power source even after stopping the backing-up of the memory. Also disclosed is a circuit for backing up memory and calendar, which has a first power source circuit to supply back-up current to both the memory and the calendar; and a second power source circuit to supply continuously back-up current to the calendar when the supply of back-up current to the memory stops due to reduction in the capacity of the first power source circuit.
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Citations
3 Claims
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1. A circuit for backing up memory and calendar, where a back-up power source for both a memory and a calendar keeps the memory stored and the calendar clocked when current supply from a main power source of a device with the memory and the calendar stops, comprising:
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a first power source circuit to supply back-up current to both the memory and the calendar; and a second power source circuit to supply continuously back-up current to the calendar when the supply of back-up current to the memory stops due to reduction in the capacity of said first power source circuit; said first power source circuit comprises a single sub-cell to back up both the memory and the calendar, a charging circuit to charge said sub-cell, and a memory back-up control circuit to control the back-up current of the memory; and said second power source circuit comprises a sub-cell capacity monitoring circuit that is inserted between said sub-cell and said memory back-up control circuit, and that stops the current supply to the memory and supplies back-up current only to the calendar when detecting that the rest of capacity of said sub-cell becomes less than a predetermined value. - View Dependent Claims (2, 3)
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Specification
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- Resources
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Current AssigneeNEC Infrontia Corporation (NEC Corporation)
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Original AssigneeNEC Corporation
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InventorsKakihara, Koji
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Primary Examiner(s)Sheikh, Ayaz R.
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Assistant Examiner(s)DHARIA, RUPAL
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Application NumberUS09/174,540Time in Patent Office792 DaysField of Search713/300-340, 713/100, 307/66, 702/58, 702/61, 702/63, 705/410, 705/401US Class Current713/300CPC Class CodesG06F 11/1441 Resetting or repowering
