Semiconductor memory device

• US 5,043,946 A
• Filed: 03/07/1990
• Issued: 08/27/1991
• Est. Priority Date: 02/09/1988
• Status: Expired due to Term

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Tanaka, Kenichi, Yamauchi, Yoshimitsu, Sakiyama, Keizo
• Primary Examiner(s): Popek, Joseph A.
• Application Number:
  US07/490,042
• Time in Patent Office: 538 Days
• Field of Search: 365/149, 365/182, 365/184, 365/185, 365/228
• US Class Current: 365/185.08
• CPC Class Codes: G11C 11/005 comprising combined but independently operative RAM-ROM, RAM-PROM, RAM-EPROM cells
• CPC Class Codes: G11C 11/404 with one charge-transfer gate, e.g. MOS transistor, per cell
• CPC Class Codes: G11C 14/00 Digital stores characterised by arrangements of cells having volatile and non-volatile storage properties for back-up when the power is down

Abstract

A semiconductor memory device comprising a DRAM, an EEPROM, a mode switch for selecting either mode of the DRAM mode and the EEPROM mode, and a transfer circuit for transferring data stored in the DRAM to the EEPROM and vice versa. The DRAM consists of one transistor and one capacitor, and one of the terminals of the capacitor is electrically isolated.

Claims

1. In a semiconductor memory device comprising:

a volatile memory means;

a non-volatile memory means;

a mode switch means for selecting either mode of a volatile memory mode in which said memory device functions as a volatile memory device and a non-volatile memory mode in which said memory device functions as a non-volatile memory device; and

a transfer means for transferring data between said volatile memory means and said non-volatile memory means in accordance with the mode selected by said switch means, the improvement existing in that said memory device further comprises a photoelectric conversion means for converting an optical signal applied thereon into an electric signal, said photoelectric conversion means being connected to said volatile memory means, said electric signal being stored in said volatile memory means.