Method and apparatus for providing security for debug circuitry
AssigneeFreescale Semiconductor, Inc.
InventorsWilliam C. Moyer, Thomas E. Tkacik
Life of this patent
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Abstract
The invention relates to debug circuitry (20) and more particularly to a method and apparatus for providing security for debug circuitry (20). In one embodiment, a plurality of non-volatile elements (38) are used in providing selective disabling and re-enabling of at least a portion of the debug circuitry (20). Authentication may also be used. The present invention may use any debug interface, including standard debug interfaces such as the JTAG debug interface defined by the IEEE.
Claims20
A method for providing security for debug circuitry, comprising:
- providing the debug circuitry, wherein the debug circuitry is enabled;
- programming a first nonvolatile element to disable the debug circuitry;
- and
- after programming the first nonvolatile element, programming a second nonvolatile element to perform one of re-enabling the debug circuitry and permanently disabling the debug circuitry.
A method for providing security for debug circuitry, comprising:
- providing the debug circuitry in a secure debug state in which the debug circuitry is capable of being selectively enabled in response to authentication;
- enabling the debug circuitry in response to authentication;
- and
- after enabling the debug circuitry in response to authentication, programming a first nonvolatile element
- after programming the first nonvolatile element, programming a second nonvolatile element, wherein, after programming the second nonvolatile element, the debug circuitry is in a re-enabled secure debug state in which the debug circuitry is capable of being selectively enabled in response to authentication.
An integrated circuit, comprising:
- debug circuitry;
- a first nonvolatile element;
- a second nonvolatile element;
- and
- debug enable circuitry which provides a debug enable indicator to the debug circuitry based on the first and second nonvolatile elements, wherein:
- the first nonvolatile element indicates whether or not the debug circuitry is in a secure debug state in which the debug circuitry can be selectively enabled in response to authentication;
- and
- the second nonvolatile element indicates whether or not to override the first nonvolatile element.
Dependencies are inferred from the claim text.