Sequential EEPROM writing apparatus which sequentially and repetitively replaces a head position pointer with a last position pointer

• US 5,689,676 A
• Filed: 11/18/1996
• Issued: 11/18/1997
• Est. Priority Date: 04/28/1988
• Status: Expired due to Term

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Nakata, Shingo, Hirose, Harumi, Takekawa, Yoshiki, Ando, Toshizumi, Isogawa, Toshiaki
• Primary Examiner(s): Coleman, Eric
• Application Number:
  US08/746,878
• Time in Patent Office: 365 Days
• Field of Search: 395/800, 395/427, 395/421.07, 395/421.08, 395/430
• US Class Current: 711/103
• CPC Class Codes: G11C 16/102 External programming circuits, e.g. EPROM programmers; In-circuit programming or reprogramming; EPROM emulators
• CPC Class Codes: G11C 16/105 Circuits or methods for updating contents of nonvolatile memory, especially with 'security' features to ensure reliable replacement, i.e. preventing that old data is lost before new data is reliably written
• CPC Class Codes: G11C 16/349 Arrangements for evaluating degradation, retention or wearout, e.g. by counting erase cycles
• CPC Class Codes: G11C 16/3495 Circuits or methods to detect or delay wearout of nonvolatile EPROM or EEPROM memory devices, e.g. by counting numbers of erase or reprogram cycles, by using multiple memory areas serially or cyclically

Abstract

A storage device incorporating an electrically erasable read only memory (EEPROM) or other data storage device having a limited number of total times of rewriting, has its useful like extended by the method of storing a pointer corresponding to the capacity of the memory, which pointer identifies a start position in the data storage device at which rewriting is to occur, and incrementing the pointer sequentially with each writing of the data storage device. The method and associated apparatus may be used to maintain a record of on-time of electronic apparatus, and/or to maintain data for correcting the white balance of a video camera under various light conditions.

Claims

1. An apparatus for storing data in memory device having a finite total number of writings comprising:

a data memory having a plurality of data areas for storing data;

a pointer memory for storing pointer information corresponding to said plurality of data areas, said pointer information identifying a beginning data area and wherein said pointer information is sequentially ordered from a head position pointer to a last position pointer; and

a control means for identifying a start in said pointer memory by said head position pointer and writing and changing the contents of said pointer memory sequentially and repetitively by replacing said head position pointer with a last position pointer.