Patents by Inventor Andrew John Merritt

Andrew John Merritt has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Asynchronously accessing the program counter values of a data processing system by applying an independent clock on the latching and scan-chain circuits
    Patent number: 6598150
    Abstract: A processing system 2 is described including a processor unit 4 and a memory 6. Diagnostic hardware 10 within the processing system 2 includes a shadow PC register 12 that stores a shadow program counter value following the true program counter value held within a program counter register 8 of the processor unit 4. The diagnostic hardware 10 is responsive to a program counter request signal from an external diagnostic system 14 to transfer a program counter value into a scan chain 16 from where it can be returned to the diagnostic system 14. The operation of the processor unit 4 is independent of any of the diagnostic operations and so true real time operation of the system may be observed and de-bugged.
    Type: Grant
    Filed: October 3, 2001
    Date of Patent: July 22, 2003
    Assignee: Arm Limited
    Inventors: Michael John Williams, Andrew John Merritt
  • Accessing diagnostic program counter value data within data processing systems
    Publication number: 20020049893
    Abstract: A processing system 2 is described including a processor unit 4 and a memory 6. Diagnostic hardware 10 within the processing system 2 includes a shadow PC register 12 that stores a shadow program counter value following the true program counter value held within a program counter register 8 of the processor unit 4. The diagnostic hardware 10 is responsive to a program counter request signal from an external diagnostic system 14 to transfer a program counter value into a scan chain 16 from where it can be returned to the diagnostic system 14. The operation of the processor unit 4 is independent of any of the diagnostic operations and so true real time operation of the system may be observed and de-bugged.
    Type: Application
    Filed: October 3, 2001
    Publication date: April 25, 2002
    Applicant: ARM Limited
    Inventors: Michael John Williams, Andrew John Merritt
  • Apparatus and method for identifying exception routines indicated by instruction address issued with an instruction fetch command
    Patent number: 6052774
    Abstract: The present invention provides a debugger interface unit for a data processing apparatus, comprising a control register having a number of fields, each field corresponding to a particular exception routine, and each field being settable to indicate that the debugger wishes to identify an access to the corresponding exception routine. Further, an exception routine catch logic is provided to receive a first signal when a processor core within the data processing apparatus issues an instruction fetch command for an exception routine, and to determine from an instruction address issued with the instruction fetch command which exception routine is being fetched. In addition, the catch logic is arranged to reference the field of the control register corresponding to the determined exception routine to determine if that field has been set, and if the field has been set, to output a breakpoint signal to the processor core.
    Type: Grant
    Filed: March 6, 1998
    Date of Patent: April 18, 2000
    Assignee: ARM Limited
    Inventors: Simon Anthony Segars, Peter Logan Harrod, Andrew John Merritt