Implantable cardiac rhythm management device incorporating a programmable watchdog timer

• US 6,604,001 B2
• Filed: 03/19/2001
• Issued: 08/05/2003
• Est. Priority Date: 03/19/2001
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Thomas, Brian P., Corcoran, Grant, Birkholz, Doug M.
• Primary Examiner(s): WOLFE JR, WILLIS RAY
• Application Number:
  US09/812,159
• Publication Number:
  US 20020133207A1
• Time in Patent Office: 869 Days
• Field of Search: 607/9, 607/17, 607/18, 607/27, 607/28, 607/30, 607/31, 607/60, 600/508, 600/515, 600/516, 600/517, 710/100, 710/107, 710/113, 710/118, 710/260, 712/248, 713/322, 713/323, 713/501
• US Class Current: 607/27
• CPC Class Codes: A61N 1/372 Arrangements in connection with the implantation of stimulators

Abstract

A cardiac rhythm management device incorporates a programmable Watchdog timer that permits more stringent time constraints to be placed upon the execution of software/firmware strings during a design phase when a deterministic model is being created. Thus, when performing real-time system engineering analysis on the model, potential imperfections in the deterministic model can be captured and resolved, resulting in a more reliable CRMD that is less likely to electronically reset once implanted in a patient.

Claims

1. A cardiac rhythm management device comprising means for sensing cardiac depolarization events;

pulse generating means for delivering cardiac stimulating pulses to the heart;

a microprocessor-based controller coupled to receive the electrical signals from the sensing means and connected in controlling relation to the pulse generating means, the microprocessor-based controller executing a program of instructions stored therein for producing control signals at timed intervals to the pulse generating means based, at least in part, on the electrical signals from the sensing means; and

a Watchdog timer in the microprocessor-based controller for monitoring instruction execution time by the microprocessor-based controller and capable of producing a Watchdog Interrupt signal when more than a predetermined period of time is required for executing one or more instructions in said program, the length of the predetermined time period being a programmable parameter.

2. The cardiac rhythm management device of claim 1 wherein the microprocessor-based controller has a normal mode and a test mode, the predetermined period of the Watchdog timer being programmable only when the microprocessor-based controller is in said test mode.

3. A method of debugging an implantable rhythm cardiac management device of the type incorporating a microprocessor-based controller and a pulse generator controlled by said microprocessor-based controller, the microprocessor configured to execute a program of instructions within predetermined time constraints, comprising the steps of:

(a) providing a counter that is coupled to receive regularly occurring clock signals from the microprocessor-based controller;

(b) including in the program of instructions counter reset instructions at predetermined points in a sequence of the instructions;

(c) resetting the counter upon execution of the counter reset instructions; and

(d) continuously comparing quantities contained in the counter with a first predetermined value for equality and generating an interrupt signal for reinitiating the microprocessor-based controller when the comparison obtains, said predetermined value being a programmable parameter.

4. The method of claim 3 wherein the first predetermined value is programmable only when the cardiac rhythm management device is in a test mode.

5. The method of claim 4 and further including the step of reprogramming the first predetermined value to a second predetermined value greater than the first predetermined value at the conclusion of operation in the test mode.