Patent US5515540A successfully refreshed from Google Patents.
US5515540A
Expired / Lapsed
US
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Microprocessor with single pin for memory wipe
Assignee: Maxim Integrated Products Inc
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Filing: 1993-12-28
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Granted: 1996-05-07
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Expires: 2013-12-28
Abstract
Abstract A nonvolatile microcontroller (or microprocessor) with improved security against tampering, including attempts at active intrusion. According to this invention, a battery-backed microcontroller includes encryption and power management functions, and is combined with a battery and a volatile semiconductor memory (e.g. an SRAM). The microcontroller supplies power to the semiconductor memory (either from a system power supply or from the battery). When a security violation is detected, the microcontroller wipes its encryption registers, and also grounds the power-output pin to the memory. This will destroy all data in the volatile memory.
Inventors
- 👤 Stephen N. Grider
- 👤 Wendell L. Little
- 👤 Michael L. Bolan
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 19:17
CPC Classifications
G; G06; G06F; G06F21/00; G06F21/70; G06F21/71; G06F21/75; G06F2221/00; G06F2221/21; G06F2221/2143
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
102 words
A nonvolatile microprocessor-controlled module, comprising: encryption circuitry, said encryption circuitry including encryption registers; power management circuitry having power input nodes; a battery, said power input nodes coupled to said battery and to an external power supply terminal; a volatile memory; security violation detectors to detect a security violation; a microcontroller coupled to supply power via said power management circuitry to said volatile memory and to control said encryption registers, said security violation detectors coupled to said microcontroller; and wherein when a security violation is detected by said security violation detectors, said security violation detectors rewrite said encryption registers to a known value.
Claim 2
Dependent Claim
102 words
A nonvolatile microprocessor-controlled module, comprising: encryption circuitry, said encryption circuitry including encryption registers; power management circuitry having power input nodes; a battery, said power input nodes coupled to said battery and to an external power supply terminal; a volatile memory; security violation detectors to detect a security violation; a microcontroller coupled to supply power via said power management circuitry to said volatile memory and to control said encryption registers, said security violation detectors coupled to said microcontroller; and wherein when a security violation is detected by said security violation detectors, said security violation detectors rewrite said encryption registers to a known value.
Claim 3
Dependent Claim
60 words
The nonvolatile microprocessor-controlled module of claim 1, further comprising: said security violation detectors emit at least one security violation signal to said microcontroller; a delay circuit coupled between said security violation detectors and said microcontroller, said delay circuit suppressing propagation of security violation detection signal(s) when said security violation detection signal(s) have a duration less than a preselected minimum duration.
Claim 4
Dependent Claim
45 words
The nonvolatile microprocessor-controlled module of claim 1, further wherein when a security violation is detected by said security violation detectors and said security violation detectors rewrite said encryption registers to a known value, said security violation detectors also cuts off power to said volatile memory.
Claim 5
Dependent Claim
29 words
The nonvolatile microprocessor-controlled module of claim 3, further wherein said security violation detectors cuts off power to said volatile memory while continuing to supply power to said encryption registers.
Claim 6
Dependent Claim
18 words
The nonvolatile microprocessor-controlled module of claim 1, wherein said volatile memory is an external memory to said microcontroller.
Claim 7
Dependent Claim
16 words
The nonvolatile microprocessor-controlled module of claim 1, wherein said volatile memory is used to store programs.
Claim 8
Dependent Claim
19 words
The nonvolatile microprocessor-controlled module of claim 1, wherein said battery is a 3 volt battery using a lithium chemistry.
Claim 9
Dependent Claim
15 words
The nonvolatile microprocessor-controlled module of claim 1, wherein said volatile memory is a CMOS SRAM.
Claim 10
Dependent Claim
23 words
The nonvolatile microprocessor-controlled module of claim 1, wherein said volatile memory is partitioned into a first memory subset and a second memory subset.
Claim 11
Dependent Claim
19 words
The nonvolatile microprocessor-controlled module of claim 1, wherein said security violation corresponds to an unauthorized tampering with specified equipment.
Claim 12
Dependent Claim
82 words
The nonvolatile microprocessor-controlled module of claim 1, further comprising: said security violation detectors emit at least one security violation signal which is received by said encryption registers, so that said encryption registers are rewritten to a known value; and a delay circuit between said security violation detectors and said encryption registers, said delay circuit suppressing propagation of security violation detection signal(s) emitted by said security violation detectors when said security violation detection signal(s) have a duration less than a preselected minimum duration.
Claim 13
Dependent Claim
82 words
The nonvolatile microprocessor-controlled module of claim 1, further comprising: said security violation detectors emit at least one security violation signal which is received by said power management circuitry, so that power to said volatile memory is cut off; and a delay circuit between said security violation detectors and said encryption registers, said delay circuit suppressing propagation of security violation detection signal(s) emitted by said security violation detectors when said security violation detection signal(s) have a duration less than a preselected minimum duration.
Claim 14
Dependent Claim
50 words
The nonvolatile microprocessor-controlled module of claim 2, further comprising: said security violation detectors emit at least one security violation signal which is received by said power management circuitry that cuts power to said volatile memory; and said delay circuit coupled between said security violation detectors and said power management circuitry.
Claim 15
Dependent Claim
52 words
The nonvolatile microprocessor-controlled module of claim 13, further comprising: said security violation detectors emit at least one security violation signal which is received by said encryption registers, so that said encryption registers are rewritten to a known value; and said delay circuit coupled between said security violation detectors and said encryption registers.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1999-05-07 | 1999-11-06 | 2000-05-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2003-05-07 | 2003-11-06 | 2004-05-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2007-05-07 | 2007-11-06 | 2008-05-07 | $7700.00 | Window Closed / Lapsed |