JPS57135500A - Data memory protecting circuit - Google Patents
Data memory protecting circuitInfo
- Publication number
- JPS57135500A JPS57135500A JP56021097A JP2109781A JPS57135500A JP S57135500 A JPS57135500 A JP S57135500A JP 56021097 A JP56021097 A JP 56021097A JP 2109781 A JP2109781 A JP 2109781A JP S57135500 A JPS57135500 A JP S57135500A
- Authority
- JP
- Japan
- Prior art keywords
- data memory
- counter
- addresses
- goes
- central controller
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Classifications
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F11/00—Error detection; Error correction; Monitoring
Abstract
PURPOSE:To protect a data memory by preventing writing permission due to a noise, by permitting writing to a data memory only when a write request signal in conformity with a certain format is received from a central controller by prescribed times. CONSTITUTION:A central controller holds all of A0-A7 at 0 and an out instruction signal is applied to a terminal 200 to reset counters 224 and 235 through a decoder 222, holding the counters in readiness for counting. Then, addresses A0- a7=(00000001) and data signals D0-D7 are inputted next to add one to the contents of the counter 224. When this counting result is coincident with an output which corresponds to the addresses D0-D7, the counter 235 goes up by one. This operation is repeated to invert the output Q of a flip-flop 237 to a level L when the counter 235 goes to a prescribed value, thereby outputting a data memory write signal.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP56021097A JPS57135500A (en) | 1981-02-16 | 1981-02-16 | Data memory protecting circuit |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP56021097A JPS57135500A (en) | 1981-02-16 | 1981-02-16 | Data memory protecting circuit |
Publications (2)
Publication Number | Publication Date |
---|---|
JPS57135500A true JPS57135500A (en) | 1982-08-21 |
JPS6230462B2 JPS6230462B2 (en) | 1987-07-02 |
Family
ID=12045362
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP56021097A Granted JPS57135500A (en) | 1981-02-16 | 1981-02-16 | Data memory protecting circuit |
Country Status (1)
Country | Link |
---|---|
JP (1) | JPS57135500A (en) |
Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS6275852A (en) * | 1985-09-30 | 1987-04-07 | Toshiba Corp | Semiconductor memory device |
JPS62286143A (en) * | 1986-06-04 | 1987-12-12 | Oki Electric Ind Co Ltd | Semiconductor memory device |
JPS6329859A (en) * | 1986-07-23 | 1988-02-08 | Sony Tektronix Corp | Memory protection circuit |
JPS63200254A (en) * | 1987-02-16 | 1988-08-18 | Nec Corp | Memory write control circuit |
JPS63221446A (en) * | 1987-02-06 | 1988-09-14 | テクトロニックス・インコーポレイテッド | Non-volatile memory protection apparatus and method |
JPS6446864A (en) * | 1987-08-17 | 1989-02-21 | Mitsubishi Electric Corp | Microcomputer |
JPH02281351A (en) * | 1989-04-21 | 1990-11-19 | Aida Eng Ltd | Memory protecting circuit |
JPH05143478A (en) * | 1991-11-20 | 1993-06-11 | Sharp Corp | Device for protecting contents of non-volatile memory |
Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS55130000A (en) * | 1979-03-26 | 1980-10-08 | Mitsubishi Electric Corp | Memory unit |
-
1981
- 1981-02-16 JP JP56021097A patent/JPS57135500A/en active Granted
Patent Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS55130000A (en) * | 1979-03-26 | 1980-10-08 | Mitsubishi Electric Corp | Memory unit |
Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS6275852A (en) * | 1985-09-30 | 1987-04-07 | Toshiba Corp | Semiconductor memory device |
JPS62286143A (en) * | 1986-06-04 | 1987-12-12 | Oki Electric Ind Co Ltd | Semiconductor memory device |
JPS6329859A (en) * | 1986-07-23 | 1988-02-08 | Sony Tektronix Corp | Memory protection circuit |
JPS63221446A (en) * | 1987-02-06 | 1988-09-14 | テクトロニックス・インコーポレイテッド | Non-volatile memory protection apparatus and method |
JPS63200254A (en) * | 1987-02-16 | 1988-08-18 | Nec Corp | Memory write control circuit |
JPS6446864A (en) * | 1987-08-17 | 1989-02-21 | Mitsubishi Electric Corp | Microcomputer |
JPH02281351A (en) * | 1989-04-21 | 1990-11-19 | Aida Eng Ltd | Memory protecting circuit |
JPH05143478A (en) * | 1991-11-20 | 1993-06-11 | Sharp Corp | Device for protecting contents of non-volatile memory |
Also Published As
Publication number | Publication date |
---|---|
JPS6230462B2 (en) | 1987-07-02 |
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