JPS6426950A - Write protecting system for memory - Google Patents
Write protecting system for memoryInfo
- Publication number
- JPS6426950A JPS6426950A JP62184274A JP18427487A JPS6426950A JP S6426950 A JPS6426950 A JP S6426950A JP 62184274 A JP62184274 A JP 62184274A JP 18427487 A JP18427487 A JP 18427487A JP S6426950 A JPS6426950 A JP S6426950A
- Authority
- JP
- Japan
- Prior art keywords
- memory
- mpu
- kept
- output
- 0fff
- 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.)
- Pending
Links
Landscapes
- Storage Device Security (AREA)
Abstract
PURPOSE:To avoid such a case where the data stored in a memory is destroyed by the runaway of an MPU by inhibiting the writing actions in response to an address signal and a switch circuit which can be externally operated. CONSTITUTION:When an MPU writes the addresses 0-0FFF while a switch 13 kept turned off, the output of an AND 7 is set at L and the output of an AND 10 is also set at L. Thus the output signal passed through an inverter 9 is set at H with the output signal of an AND 6 kept at H. As a result, the inverse of CS terminal of a RAM 1 is kept at H even though the MPU gives accesses to the addresses 0-0FFF. Thus no data could be written into the RAM 1.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP62184274A JPS6426950A (en) | 1987-07-23 | 1987-07-23 | Write protecting system for memory |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP62184274A JPS6426950A (en) | 1987-07-23 | 1987-07-23 | Write protecting system for memory |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPS6426950A true JPS6426950A (en) | 1989-01-30 |
Family
ID=16150451
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP62184274A Pending JPS6426950A (en) | 1987-07-23 | 1987-07-23 | Write protecting system for memory |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS6426950A (en) |
-
1987
- 1987-07-23 JP JP62184274A patent/JPS6426950A/en active Pending
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