Control circuit for a microcontroller

• US 6,408,170 B1
• Filed: 10/02/1998
• Issued: 06/18/2002
• Est. Priority Date: 10/08/1997
• Status: Expired due to Fees

• Current Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Original Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Inventors: Schmidt, Thomas, Knobl, Karl-Heinz
• Primary Examiner(s): Kuntz, Curtis
• Assistant Examiner(s): Taylor, Barry W
• Application Number:
  US09/165,685
• Time in Patent Office: 1,355 Days
• Field of Search: 701/36, 701/29, 701/33, 700/31, 700/82, 700/79, 340/825.31, 340/425.5, 340/568, 340/687, 340/426, 455/345, 455/344, 455/343, 455/456, 307/10.1, 702/186, 714/55, 713/323-324
• US Class Current: 455/344
• CPC Class Codes: G06F 11/0739 in a data processing system embedded in automotive or aircraft systems
• CPC Class Codes: G06F 11/0757 by exceeding a time limit, i.e. time-out, e.g. watchdogs
• CPC Class Codes: H04W 52/0229 where the received signal is a wanted signal
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A description is given of a control circuit situated outside a microcontroller, which control circuit serves to control, support and monitor the microcontroller. This is achieved in that function signals are supplied to the control circuit (2), with which function signals presettable function modes of a device (12, 13, 14) are associated, which device is controlled by said microcontroller (1), in that the control circuit (2) supplies a read-request signal to the microcontroller (1) when the function signals change, which read-request signal induces the microcontroller (1) to evaluate the changed external signal and/or read the data associated with said signal, and in that the control circuit (2), in case the microcontroller (1) is in an inactive state when the function signals change, supplies a reset signal to this microcontroller prior to supplying the read-request signal, which reset signal brings the microcontroller (1) into an active state, and after supplying the reset signal, the control circuit activates the watchdog circuit.

Claims

1. A control circuit for controlling, supporting and monitoring a microcontroller, which control circuit is built up outside the microcontroller, which is resettable by means of the control circuit, and which control circuit includes a watchdog circuit, wherein function signals are supplied to the control circuit from various microprocessor controlled devices with which function signals'"'"'presettable function modes of said devices are associated in that the control circuit supplies a read-request signal to the microcontroller when it determines that the function signals change, which read-request signal induces the microcontroller to evaluate the changed function signal and read data associated with said signal, and in that the control circuit, in case the microcontroller is in an inactive state and not responsive during the time when the function signals change, supplies a reset signal to this microcontroller prior to supplying the read-request signal, which reset signal brings the microcontroller into an active state, and after supplying the reset signal to the microprocessor, the control circuit activates the watchdog circuit.

2. A control circuit as claimed in claim 1, wherein the control circuit and the microcontroller are arranged in a car radio which is controlled through the microcontroller, and in that the predefined external functions are functions of the car radio, in particular, an activated switching voltage, a triggered depression of a key on the car radio, a cassette inserted into the car radio or fitting an operating element of the car radio.

3. A control circuit as claimed in claim 1, wherein after a reset signal has been supplied to the microcontroller, at least during a predetermined time period, no further reset signals are supplied to said microcontroller.

4. A control circuit as claimed in claim 1, wherein the watchdog circuit is deactivated after the microcontroller has been transferred to the inactivate state by means of said microcontroller, and in that, after the watchdog circuit has been triggered, it supplies maximally five times a reset signal to the microcontroller when said microcontroller is in the active state.

5. A control circuit as claimed in claim 1, wherein in the control circuit an internal monitoring of an internal clock signal takes place, and in case of a drop-out of the internal clock signal, a corresponding error message is supplied to the microcontroller.

6. A control circuit as claimed in claim 1, wherein the control circuit comprises a time-dependent counter whose starting value can be changed and whose current value is compared to an externally presettable value, and if the counter value and the presettable value correspond to each other, a preselectable function of the microcontroller is triggered.

7. A control circuit as claimed in claim 1, wherein the control circuit comprises an output for an intermittent signal whose blinking interval, in the case of errors in one of:

the control circuit and the microcontroller, which are changed in a manner associated with the type of error.

8. A control circuit as claimed in claim 1, wherein the control circuit and the microcontroller are accommodated in a car radio, in that the control circuit comprises a voltage-detection input which, if in the on-state of the car radio is switched to the power supply voltage of the car radio and, in the off-state, to the reference voltage of the car radio, and if in that the control circuit evaluates the voltage-detection input in such a manner that a theft is recognised and reported to the microcontroller when the voltage-detection input is at neither of these two voltages.

9. A control circuit as claimed in claim 1, wherein to detect a decrease of the power supply voltage of the device with respect to the nominal value, the control circuit supplies a timer signal to the microcontroller at intervals which are determined by means of a counter arranged in the control circuit, thus causing the microcontroller to trigger a measurement of the height of the power supply voltage.

10. A control circuit as claimed in claim 1, wherein the power supply voltage of the microcontroller can be switched by means of the control circuit, and in that the microcontroller can be switched to the inactive state by switching off the power supply voltage by means of the control circuit.

11. A method for controlling, supporting and monitoring a microcontroller, the method comprising:

providing a control circuit which includes a watchdog circuit built up outside the microcontroller, said microcontroller resettable by means of the control circuit;

supplying function signals to the control circuit from devices controlled by the microcontroller, with which function signals presettable function modes of said devices are associated;

supplying a read-request signal to the microcontroller by the control unit when the received function signals change, which read-request signal induces the microcontroller to evaluate the changed function signal and read data associated with said read-request signal;

supplying a reset signal to the microcontroller by the control circuit prior to supplying the read-request signal thereto, in case the microcontroller is in an inactive state when the function signals change, the reset signal bringing the microcontroller into an active state; and

activating the watchdog circuit after supplying the reset signal to the microcontroller by the control circuit.

12. A system for controlling, supporting and monitoring a microcontroller, the system comprising:

a control circuit means which includes a watchdog circuit means built up outside the microcontroller, said microcontroller resettable by means of the control circuit means;

means for supplying function signals from devices controlled by the microcontroller to the control circuit means, with which function signals presettable function modes of said devices are associated;

means for supplying a read-request signal to the microcontroller by the control circuit means when the function signals change, which read-request signal induces the microcontroller to evaluate the changed function signal and read data associated with said read-request signal;

means for supplying a reset signal to the microcontroller by the control circuit means prior to supplying the read-request signal thereto, in case the microcontroller is in an inactive state when the function signals change, the reset signal bringing the microcontroller into an active state; and

means for activating the watchdog circuit means after supplying the reset signal to the microcontroller by the control circuit means.