Nonvolatile realtime clock calendar module

Details Nonvolatile realtime clock calendar module Nonvolatile realtime clock calendar module

1984-12-31

1987-10-20

Krass, Errol A.

Boots, shoes, and leggings

34087002, 365229, 371 66, G08B 2300, G11C 800

Patent

active

047018585

ABSTRACT:
A circuit module for general use in microcomputer based systems, such as time-of-use electronic utility meters, which maintains realtime clock calendar information even through long term power outages of 12 hours or more without the use of batteries. Realtime computations are protected by combining a very low power realtime clock calendar integrated circuit with a large capacitor as a secondary power source. The circuit module provides a reference clock calendar for the associated microcomputer. The module includes a capacitor charging circuit deriving power from a primary power source, a crystal oscillator time base circuit and a memory read/write protect circuit. During a power failure the capacitor, which is disconnected from the primary power source, supplies to the module the necessary power to maintain valid realtime computations. At the end of the outage when line power returns, the capacitor is quickly recharged and the non-degraded realtime clock calendar database is available to be transferred to the associated microcomputer to re-establish realtime processing.

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patent: 4449205 (1984-05-01), Hoffman
patent: 4466074 (1984-08-01), Jindrick et al.
"1-Farad Capacitors for CMOS Memory Backup", Electronic Product Design, Aug. 1982, p. 9.

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