ELECTRONIC CONTROL DEVICE

• US 20130067287A1
• Filed: 09/13/2012
• Published: 03/14/2013
• Est. Priority Date: 09/14/2011
• Status: Active Grant

• Current Assignee: Hitachi Astemo Ltd. (Hitachi, Ltd.), Honda Motor Co., Ltd. (Honda Motor Company)
• Original Assignee: Keihin Corporation (Hitachi, Ltd.), Honda Motor Co., Ltd. (Honda Motor Company)
• Inventors: YOSHIKAWA, Taku, DAIBO, Shinichi, KOBATA, Yuichi, YAMADA, Takeshi
• Granted Patent: US 8,996,927 B2
• Time in Patent Office: Days
• US Class Current: 714/47.1
• CPC Class Codes: G06F 11/0757 by exceeding a time limit, i.e. time-out, e.g. watchdogs
• CPC Class Codes: H02J 7/0029 with safety or protection devices or circuits

Abstract

An electronic control device includes: a processing unit that performs a predetermined process in accordance with a program; a watchdog timer that includes a time counter reset by a pulse signal output at a given period from the processing unit and outputs a signal having levels inverted depending on whether an overflow occurs; and a latch circuit that latches the signal output from the watchdog timer and outputs a signal obtained through the latching as a first output enable signal. The processing unit stops the output of the pulse signal, when diagnosing a malfunction of the watchdog timer, and diagnoses the malfunction of the watchdog timer based on the first output enable signal output from the latch circuit, after stopping the output of the pulse signal.

Claims

1. An electronic control device comprising:

a processing unit that performs a predetermined process in accordance with a program;

a watchdog timer that includes a time counter reset by a pulse signal output at a given period from the processing unit and outputs a signal having levels inverted depending on whether an overflow occurs; and

a latch circuit that latches the signal output from the watchdog timer and outputs a signal obtained through the latching as a first output enable signal,

wherein the processing unit stops the output of the pulse signal, when diagnosing a malfunction of the watchdog timer, and diagnoses the malfunction of the watchdog timer based on the first output enable signal output from the latch circuit, after stopping the output of the pulse signal.

2. The electronic control device according to claim 1, further comprising:

an AND circuit that calculates a logical AND of the first output enable signal output from the latch circuit and a second output enable signal output from the processing unit and outputs a signal indicating the calculation result as a final output enable signal,

wherein the processing unit diagnoses the malfunction of the watchdog timer based on the first output enable signal output from the latch circuit and the output enable signal output from the AND circuit, after stopping the output of the pulse signal.

3. The electronic control device according to claim 1, further comprising:

an AND circuit that calculates a logical AND of the first output enable signal output from the latch circuit and a second output enable signal output from the processing unit and outputs a signal indicating the calculation result as a final output enable signal; and

a three-state buffer that is provided between the processing unit and an output interface and outputs a signal output from the processing unit to the output interface in accordance with the output enable signal output from the AND circuit,

wherein the processing unit diagnoses the malfunction of the watchdog timer based on the first output enable signal output from the latch circuit and the output signal output from the three-state buffer, after stopping the output of the pulse signal.

4. The electronic control device according to claim 1, wherein the latch circuit is reset when any one of an activation ignition signal or a reset signal of the processing unit is input.