JPH07128461A - Time mismeasurement preventer - Google Patents

Abstract

PURPOSE:To prevent mismeasurement of time by detecting a trailing edge of pulse signal and by judging the state of a pulse signal of a current interruption port on every interruption so as to cancel noise if present in an input signal. CONSTITUTION:A tau signal (pulse signal) is outputted from an engine electronic controller 1 into a CRT electronic controller 2, and a fuel injection amount is measured from the fall time of signal. First, the controller 2 detects a trailing edge of a waveform-shaped tau signal to judge whether or not it is a trailing edge interruption. When it is a trailing edge interruption, it stores a trailing edge free-run counter value to store a tau signal fall and sets a state of trailing edge standby to stand by a tau signal rise. When a tau signal rises with the lapse of time, this device calculates and stores an integrated value of fuel injection from a preceding integrated value of fuel injection time and a free-run counter value, so that a state of trailing edge standby is set to stand by a tau signal fall.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an erroneous measurement when an electronic control unit (hereinafter referred to as an ECU) equipped with a timer and a CPU measures time.

[0002]

2. Description of the Related Art Conventionally, when measuring time (pulse falling time or the like) in an ECU, a rising edge or a falling edge of an input signal is detected and interrupt processing is performed. When this is realized by one port, for example, an interrupt is issued when the falling edge of a signal is detected, the falling free-run counter is stored, and the rising edge wait is set. Then, when a rising edge is detected, an interrupt is applied, the rising free-run counter is stored, and the falling time of the signal (hereinafter referred to as Low time) is obtained by calculating the difference between the two free-run counters.

[0003]

However, in the above-mentioned conventional apparatus, as shown in FIG. 3, when noise is input to the signal, its Low time is too short. The signal rises while setting to wait for rising edge. Therefore, at the next signal rise, the ECU changes the Low time (T1) that is different from the actual Low time (T2).
There is a problem of measuring.

Therefore, the present invention has been made in view of the above problems. Even if a signal input through one input port has noise or the like, it is canceled.
It is an object of the present invention to provide an erroneous time measurement prevention device capable of preventing erroneous time measurement.

[0005]

In order to achieve the above object, the time erroneous measurement preventing device of the present invention detects a change from a first state to a second state of a pulse signal input through one input port. Then, the interrupting means for making an interrupt, the storing means for storing the state of the pulse signal as the second state when interrupted by the interrupting means, and the state of the pulse signal in the storing means as the second state. When it is stored, it is determined whether the pulse signal input to the input port is in the second state, and the standby unit that waits for the change of the pulse signal from the second state to the first state. And a changing means for changing the standby of the change of the pulse signal by the standby means so as to wait for the change from the first state to the second state when the determination means makes a negative determination. thing And it features.

[0006]

According to the present invention having the above construction, the judging means judges whether or not the state of the pulse signal input to the input port is the second state, and if the judgment is negative, the changing means causes the pulse signal of the waiting means to The change waiting is changed to wait for the change from the first state to the second state. That is, each time the pulse signal changes from the first state to the second state and an interrupt occurs, the determination means determines the current state of the pulse signal of the interrupt port, and if the logic does not match (the pulse signal If the state of the pulse signal input to the input port is the first state in spite of the standby from the two states to the first state), wait for the change of the pulse signal from the first state to the second state.
Since the change is made so as to wait for the change to the state, even if noise or the like is input, it is canceled.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. In this embodiment, the present invention is used in a fuel injection device for a vehicle. That is, as shown in the electrical system diagram of FIG. 1, from the engine ECU 1 to the CRT (Cathode Ray Tube)
The τ signal is output to the ECU 2, the output destination CRTECU 2 waveform-shapes the pulse signal as shown in FIG. 2, the LOW time of the waveform-shaped τ signal is measured, and the fuel injection amount is calculated based on the LOW time. I try to measure it.

Next, the processing in the CRTECU 2 of this embodiment will be described with reference to the flowchart of FIG. First, in step 100, it is determined whether or not a falling edge interrupt is detected by detecting the falling edge of the waveform-shaped τ signal. If it is a fall interrupt, the process proceeds to steps 110 and 120, where the fall free-run counter A is stored to store the fall of the τ signal, and the rising edge waiting state is set to wait for the rise of the τ signal. . Next, in step 130, it is determined whether the input port is Low. Normally, when the τ signal falls, the determination is Yes because the input port is Low, and the process directly returns.

After that, when the edge of the .tau. Signal rises after a lapse of time, the determination in step 100 becomes No and the process proceeds to step 150. In step 150, the fuel injection time integrated value is calculated by the previous injection time integrated value + (current free-run counter value-A). Here, the current free-run counter value is a value obtained by incrementing the clock pulse CK output from the timer provided in the ECU to the CPU since the ignition was turned on. When the fuel injection time integrated value is calculated, step 16
The process proceeds to 0 and the calculated fuel injection time integrated value is stored.
This stored value is used as the previous injection time integrated value in the next step 150. When the integrated value of the fuel injection time is stored, in step 170, a falling edge waiting state is set to wait for the falling of the τ signal, and then the process returns.

Next, while repeating the above processing,
A case where noise is input to the τ signal as shown in FIG. 3 will be described. First, when noise is input to the τ signal, the determination in step 100 becomes Yes. Then, after performing the processing of steps 110 and 120 as described above, the process proceeds to step 130. However, since the time during which noise is input is too short, the port is already High before the processing of step 130. . Therefore, the determination in step 130 is No, and the process proceeds to step 140 to set the rising edge waiting state.

As a result, in this embodiment, even if the LOW time is too short when the noise is input, the noise input can be canceled and the rising edge waiting state can be set. That is, in this embodiment, each time a falling edge interrupt is input, the signal level of the current interrupt port is determined in step 130, and if the logic does not match (when the port is High despite the rising edge wait state). ), The rising edge of noise or the like is canceled, so even if noise or the like is input, a Low time different from the actual Low time (T2) shown in FIG.
The time (T1) is no longer measured.

[0012]

As described above, according to the present invention, when the determination means makes a negative determination, the standby of the pulse signal is changed, so that the input of noise or the like can be carried out and the false detection of time can be prevented. It has an excellent effect that it can be done.

[Brief description of drawings]

FIG. 1 is an electrical system diagram showing signal transmission in an embodiment of the present invention.

FIG. 2 is a time chart showing a normal τ signal.

FIG. 3 is a time chart showing an abnormal τ signal.

FIG. 4 is a flowchart showing a process in CRTECU2.

[Explanation of symbols]

 1 Engine ECU 2 CRT ECU

Claims (1)

[Claims] 1. An interrupt means for detecting a change from a first state to a second state of a pulse signal input through one input port and interrupting the pulse signal, and a pulse signal when the interrupt means interrupts the interrupt. Storing the state of No. 2 as the second state, and changing the state of the pulse signal from the second state to the first state when the state of the pulse signal is stored as the second state in the storage unit. Waiting means for waiting, a judging means for judging whether or not the state of the pulse signal input to the input port is the second state, and a negative judgment by the judging means, the pulse by the waiting means. An erroneous time measurement prevention apparatus comprising: a changing unit that changes the standby for a signal change to a standby for a change from the first state to the second state.