US4698750A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Security for integrated circuit microcomputer with EEPROM
Assignee: NXP USA Inc
•
Filing: 1984-12-27
•
Granted: 1987-10-06
•
Expires: 2004-12-27
Abstract
Abstract An integrated circuit microcomputer with EEPROM has a limited number of modes for operation. In at least first and second modes, the inner workings of the microcomputer, including the contents of the EEPROM, can be read externally from the microcomputer. An EEPROM security bit, when set, prevents the first mode from being entered and causes the EEPROM to be erased when the second mode is entered. The EEPROM is also erased if the security bit is erased.
Inventors
- 👤 Brian F. Wilkie
- 👤 Michael Gallup
- 👤 John Suchyta
- 👤 Kuppuswamy Raghunathan
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 03:11
CPC Classifications
G; G06; G06F; G06F12/00; G06F12/14; G06F12/1416; G06F12/1425; G06F12/1433
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
140 words
In an integrated circuit microcomputer having on-board memory including an EEPROM and having detection means for detecting a request for a mode of operation of the microcomputer and characterized as having a first mode of operation in which contents of the EEPROM can be read externally from the microcomputer, and a second mode of operation in which the contents of the EEPROM cannot be externally read from the microcomputer, means for securing the contents of the on-board memory, comprising: an EEPROM security bit which can be set after the EEPROM has been loaded and which is erasable only if the EEPROM is also erased; and first means, coupled to the detection means, for erasing the contents of the EEPROM in response to the detection means receiving a request for the first mode of operation when the security bit is set.
Claim 2
Dependent Claim
140 words
In an integrated circuit microcomputer having on-board memory including an EEPROM and having detection means for detecting a request for a mode of operation of the microcomputer and characterized as having a first mode of operation in which contents of the EEPROM can be read externally from the microcomputer, and a second mode of operation in which the contents of the EEPROM cannot be externally read from the microcomputer, means for securing the contents of the on-board memory, comprising: an EEPROM security bit which can be set after the EEPROM has been loaded and which is erasable only if the EEPROM is also erased; and first means, coupled to the detection means, for erasing the contents of the EEPROM in response to the detection means receiving a request for the first mode of operation when the security bit is set.
Claim 3
Dependent Claim
19 words
The microcomputer of claim 1, wherein the first means erases the security bit after the EEPROM has been erased.
Claim 4
Dependent Claim
32 words
The microcomputer of claim 2 further having an on-board RAM, wherein the first means erases the RAM in response to entering the first mode of operation when the security bit is set.
Claim 5
Dependent Claim
58 words
The microcomputer of claim 3 further having a third mode of operation in which the contents of the EEPROM can be read externally from the microcomputer, wherein the means for securing the contents of the on-board memory further comprises: second means for preventing the microcomputer from entering the third mode of operation when the security bit is set.
Claim 6
Dependent Claim
58 words
The microcomputer of claim 1 further having a third mode of operation in which the contents of the EEPROM can be read externally from the microcomputer, wherein the means for securing the contents of the on-board memory further comprises: second means for preventing the microcomputer from entering the third mode of operation when the security bit is set.
Claim 7
Dependent Claim
19 words
The microcomputer of claim 5, wherein the first means erases the security bit after the EEPROM has been erased.
Claim 8
Dependent Claim
121 words
In an integrated circuit microcomputer having on-board memory including an EEPROM and having detection means for detecting a request for a mode of operation of the microcomputer and characterized as having a first mode of operation in which contents of the EEPROM can be read externally from the microcomputer, and a second mode of operation in which the contents of the EEPROM cannot be read externally from the microcomputer, a method of securing the contents of the on-board memory, comprising: providing an EEPROM security bit which can be set after the EEPROM has been loaded; loading the EEPROM; setting the security bit; and erasing the EEPROM in response to the detection means receiving a request for the first mode of operation.
Claim 9
Dependent Claim
121 words
In an integrated circuit microcomputer having on-board memory including an EEPROM and having detection means for detecting a request for a mode of operation of the microcomputer and characterized as having a first mode of operation in which contents of the EEPROM can be read externally from the microcomputer, and a second mode of operation in which the contents of the EEPROM cannot be read externally from the microcomputer, a method of securing the contents of the on-board memory, comprising: providing an EEPROM security bit which can be set after the EEPROM has been loaded; loading the EEPROM; setting the security bit; and erasing the EEPROM in response to the detection means receiving a request for the first mode of operation.
Claim 10
Dependent Claim
17 words
The method of claim 7 further comprising: erasing the security bit after the EEPROM has been erased.
Claim 11
Dependent Claim
41 words
The method of claim 8 further comprising: checking the EEPROM to verify that it has been erased before erasing the security bit; and preventing the erasure of the security bit if any of the EEPROM which was checked was not erased.
Claim 12
Dependent Claim
44 words
The method of claim 9 futher comprising: providing the microcomputer with a third mode of operation in which the contents of the EEPROM can be externally read; and preventing the microcomputer from entering the third mode of operation when the security bit is set.
Claim 13
Dependent Claim
30 words
The method of claim 10 further comprising: providing an on-board RAM; and erasing the RAM in response to entering the first mode of operation when the security bit is set.
Claim 14
Dependent Claim
127 words
In an integrated circuit microcomputer having on-board memory including an EEPROM and a ROM and having detection means for detecting a request for a mode of operation of the microcomputer and characterized as having a first mode of operation in which contents of the EEPROM can be read externally from the microcomputer, and a second mode of operation in which the contents of the EEPROM cannot be read externally from the microcomputer, a method of securing the contents of the on-board memory, comprising: providing an EEPROM security bit which can be set after the EEPROM has been loaded; loading the ROM with a program which causes the microcomputer to erase the EEPROM in response to the detection means receiving a request for the first mode of operation.
Claim 15
Dependent Claim
127 words
In an integrated circuit microcomputer having on-board memory including an EEPROM and a ROM and having detection means for detecting a request for a mode of operation of the microcomputer and characterized as having a first mode of operation in which contents of the EEPROM can be read externally from the microcomputer, and a second mode of operation in which the contents of the EEPROM cannot be read externally from the microcomputer, a method of securing the contents of the on-board memory, comprising: providing an EEPROM security bit which can be set after the EEPROM has been loaded; loading the ROM with a program which causes the microcomputer to erase the EEPROM in response to the detection means receiving a request for the first mode of operation.
Claim 16
Dependent Claim
30 words
The method of claim 12 wherein the program loaded into the ROM is further characterized as causing the microcomputer to erase the security bit after the EEPROM has been erased.
Claim 17
Dependent Claim
127 words
In an integrated circuit microcomputer having on-board memory including an EEPROM and having detection means for detecting a request for a mode of operation of the microcomputer and characterized as having a first mode of operation in which contents of the EEPROM can be read externally from the microcomputer and a second mode of operation in which the contents of the EEPROM cannot be read externally from the microcomputer, means for securing the contents of the on-board memory comprising: an EEPROM security bit which can be set after the EEPROM has been loaded; a ROM containing a program which causes the microcomputer to erase the EEPROM in response to the detection means receiving a request for the first mode of operation when the security bit is set.
Claim 18
Dependent Claim
127 words
In an integrated circuit microcomputer having on-board memory including an EEPROM and having detection means for detecting a request for a mode of operation of the microcomputer and characterized as having a first mode of operation in which contents of the EEPROM can be read externally from the microcomputer and a second mode of operation in which the contents of the EEPROM cannot be read externally from the microcomputer, means for securing the contents of the on-board memory comprising: an EEPROM security bit which can be set after the EEPROM has been loaded; a ROM containing a program which causes the microcomputer to erase the EEPROM in response to the detection means receiving a request for the first mode of operation when the security bit is set.
Claim 19
Dependent Claim
29 words
The microcomputer of claim 14 wherein the ROM is further characterized by the program therein causing the microcomputer to erase the security bit after the EEPROM has been erased.
Claim 20
Dependent Claim
40 words
The microcomputer of claim 15 further having an on-board RAM, wherein the ROM is further characterized by the program therein causing the microcomputer to erase the RAM in response to entering the first mode when the security bit is set.
Claim 21
Dependent Claim
54 words
The microcomputer of claim 16 further having a third mode of operation in which the contents of the EEPROM can be read externally, wherein the means for securing the contents of the on-board memory further comprises: means for preventing the microcomputer from entering the third mode of operation when the security bit is set.
Claim 22
Dependent Claim
54 words
The microcomputer of claim 14 further having a third mode of operation in which the contents of the EEPROM can be read externally, wherein the means for securing the contents of the on-board memory further comprises: means for preventing the microcomputer from entering the third mode of operation when the security bit is set.
Claim 23
Dependent Claim
29 words
The microcomputer of claim 18 wherein the ROM is further characterized by the program therein causing the microcomputer to erase the security bit after the EEPROM has been erased.
References Cited (Backward Citations)
US4005386A
Cited
US4139893A
Cited
US4430709A
Cited
WO1982002274A1
Cited
US4521852A
Cited
US4521853A
Cited
US4590552A
Cited
US4603381A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1990-10-05 | 1991-04-06 | 1991-10-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-10-05 | 1995-04-06 | 1995-10-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-10-05 | 1999-04-06 | 1999-10-06 | $7700.00 | Window Closed / Lapsed |