JP3753797B2 - Microcomputer device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a microcomputer device suitable as a one-chip microcomputer having a number of terminal pins arranged close to each other, and more particularly to a microcomputer device having a function of diagnosing a short-circuit failure between adjacent ports.
[0002]
[Prior art]
In recent years, the distance between terminal pins of so-called one-chip microcomputers has become extremely narrow due to demands for miniaturization, weight reduction, and high-density mounting, and 0.5 mm or less have also appeared. Here, the one-chip microcomputer includes not only a CPU but also peripheral devices such as memories such as ROM and RAM, input / output ports, communication ports, timers, LCD drivers, MMUs, DMACs, and A / D converters. A microcomputer mounted on a single chip.
[0003]
Conventionally, this type of one-chip microcomputer is diagnosed with a pin-to-pin short-circuit fault by visual inspection by an operator during inspection at the time of manufacture, or visual inspection using an optical device, or electrical continuity by a predetermined inspection device. It was customary to do this by testing. In other words, this kind of one-chip microcomputer may cause short-circuiting between terminal pins during soldering work, so let's diagnose this by visual inspection of the operator or image processing based on video obtained from a video camera. It is what.
[0004]
[Problems to be solved by the invention]
However, in this kind of one-chip microcomputer, even if it is normal in the inspection process at the time of manufacture, the foreign matter between the terminal pins once shipped, etc. In some cases, a short-circuit failure may occur. Therefore, it has been desired that this type of pin-to-pin short-circuit failure can be accurately diagnosed not only at the manufacturing stage but also after shipment.
[0005]
The present invention has been made based on the above-described technical background, and the object of the present invention is to prevent short-circuit faults between adjacent terminal pins in this type of one-chip microcomputer from being shipped not only at the manufacturing stage. This is to enable accurate diagnosis even after being performed.
[0006]
[Means for Solving the Problems]
The invention described in claim 1 of this application is that the first port in which a pair of adjacent ports are used as input ports, and an input port and an output port can be arbitrarily set through a program. The microcomputer device is configured by a second port that is an input / output port that can be switched to the first port, and the first port and the second port are electrically independent from each other. The system program of the computer device includes a diagnostic process for diagnosing a short-circuit failure between the pair of adjacent ports, and the diagnostic process changes the second port from the input port to the output port. Port function switching processing for switching, test signal transmission processing for transmitting a predetermined test signal from the second port switched to the output port, and the test signal Reads the signal of the first port in the state where There has been transmitted, it comprises a signal state determination process of determining whether or not changes hung on the test signal, A test signal is output from a port in which the second port is switched to an output port, and the period of the signal source input to the first port is such that the period of the test signal can be identified. The microcomputer apparatus is characterized by being set shorter .
[0013]
Such a short-circuit failure between a pair of adjacent ports generally causes a foreign object to be present between the terminal pins connected to these ports, a solder bridge to occur, or the terminal pins to receive physical stress or thermal stress. This often occurs when the two parts deform and come into contact with each other.
[0014]
According to the first aspect of the present invention, foreign matter or the like is mixed between the pair of terminal pins, the two are short-circuited, or they are deformed and contacted by receiving physical or thermal stress. If the test signal is sent from one port, the signal of the other port will change according to the test signal. Thus, it is possible to appropriately diagnose not only at the manufacturing stage but also after shipment. In addition, since the port that was originally used as the input port is switched to the output port and then the test signal is sent from the output port, the port that was originally used as the output port is used. Unlike the case of outputting a test signal, the test signal transmission destination device is hardly adversely affected. In addition, even when there is a normal input signal, this type of short-circuit fault diagnosis is possible, and if a short-circuit fault occurs between any of the terminals during specific control using a microcomputer, Appropriate responses can be taken.
[0018]
According to a second aspect of the present invention, the microcomputer device is a one-chip microcomputer in which terminal pins corresponding to the respective ports are arranged close to each other. In computer equipment.
[0019]
According to the invention described in claim 2 , the reliability of this kind of one-chip microcomputer can be remarkably improved.
[0020]
The invention according to claim 3 of the present application is characterized in that a predetermined abnormality process is executed in response to a diagnosis that a short circuit between a pair of adjacent ports is short-circuited in the diagnosis process. A microcomputer apparatus according to claim 1.
[0021]
According to the third aspect of the present invention, when it is diagnosed that the adjacent ports are short-circuited, it is possible to immediately execute the abnormality process and take appropriate measures. Here, “abnormal processing” includes processing such as displaying or notifying the fact to the outside, stopping the execution of control, and transferring the control right to another microcomputer. Will be.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[0023]
FIG. 1 shows a circuit configuration of a vehicle electronic control device (hereinafter referred to as ECU) to which the present invention is applied. As shown in the figure, a one-chip microcomputer 2 to which the present invention is applied is mounted on a circuit board 1 of the ECU. As is well known, this type of one-chip microcomputer 2 is accommodated in a multi-pin package such as a QFP package, and a large number of input / output ports are provided on the outer periphery thereof. In FIG. 1, only two ports P1 and P2 arranged adjacent to each other among these input / output ports are shown. These ports P1 and P2 are both configured as input / output ports, as will be described in detail later.
[0024]
The switches SW1 and SW2 symbolically indicate arbitrary signal sources, and input signals generated from these switches SW1 are supplied to external input terminals T1 and T2 provided on the circuit board 1 of the ECU. The The input signals supplied to these external input terminals T1 and T2 are further supplied to the ports P1 and P2 of the one-chip microcomputer 2 described above after passing through the interface circuits IF1 and IF2. That is, these two ports P1 and P2 are used as input ports.
[0025]
The interface circuits IF1 and IF2 have the same configuration, and include a pull-up resistor R2, a low-pass filter composed of a resistor R1 and a capacitor C, and an overvoltage protection circuit composed of diodes D1 and D2. ing.
[0026]
Next, a specific circuit configuration for realizing the input / output port is shown in FIG. As shown in the figure, the entire input / output port circuit is composed of an input circuit and an output circuit which are in antiparallel with each other. That is, the input circuit responds to the strobe signal WRout with the input gate 4 for reading the signal input from the port Pn into the internal bus 3 in response to the strobe signal RD and the signal sent on the internal bus 3. And an output latch 5 for latching it and outputting it to the port Pn. These input / output circuits are configured to alternatively operate by switching means using the port mode register 6, the mode switching gate 7, and the tristate buffer 8.
[0027]
That is, a port mode flag is written in the port mode register 6 in response to the strobe signal WRpm. When the content of the port mode flag is “1”, the port mode switching gate 7 is opened and the tri-state buffer When the port mode flag is “0”, the mode switching gate 7 is closed and the tristate buffer is realized. When 8 is activated, the function as an output port is realized.
[0028]
The control for writing the port mode flag to the port mode register 6 can be performed by using a predetermined instruction on the program.
[0029]
Next, on the premise of the circuit configuration shown in FIG. 1 and the circuit configuration of the input / output port shown in FIG. 2, the details of the diagnosis processing according to the present invention will be described with reference to the flowcharts of FIG. 3 and FIG. This will be described with reference to the chart.
[0030]
First, an overview of the diagnostic processing according to the present invention is shown in the general flowchart of FIG.
[0031]
This diagnosis process can be executed in the initialization process immediately after the power is turned on, or at any time during the execution of the control program. The entire process is a process of switching the mode of one of the ports P2 to the output mode among the adjacent ports P1 and P2 (step 301), and the output logic of the port P2 is periodically changed in that state. Then, a process of sending a predetermined test signal (step 302), a process of reading the signal of P1 which is the other port in that state and examining its input logic (step 303), and the result of the input logic of port P1 Is determined according to the output logic of the port P1 (step 304).
[0032]
In the flowchart shown in the figure, these processes are simply arranged in series and executed in time series. However, in actuality, these processes are performed by changing the input logic of the port P1 to the output logic of the port P2. It is repeatedly executed until it is determined that the change has occurred.
[0033]
Therefore, this will be described in detail with reference to the flowchart of FIG. In the figure, when the process is started, the value of the counter C is reset to zero (step 401), and then "H" and "L" are alternately output from the port P2 every predetermined time (steps 402, 404). ) Each time the process of determining the level of the port P1 (steps 403 and 405) is performed by incrementing the value of the counter C by 1 (step 406), until the value of the counter C reaches “5” (step 406). 407 NO) Repeat.
[0034]
Then, as shown in FIG. 5, a pulse train that is alternately switched between “H” and “L” is output from the port P2 at a minute time interval. The output period of this pulse train is set to be sufficiently shorter than the period of the signal obtained in the normal time from the signal source symbolized by the switch SW1. That is, even if some signal is obtained from the switch SW1 in the normal state, such a signal can be sufficiently distinguished from the minute width pulse train as the test signal.
[0035]
And, in such a state where a minute width pulse train is output from the port P2,
When the state of the port P1 is determined, the signal at the port P1 does not change in the normal state or only the signal at the normal time is obtained, whereas the broken line 9 in FIG. In addition, when a short circuit failure occurs between the ports P1 and P2, the input logic of the port P1 changes according to the output logic of the port P2. If the above is continued (YES in step 407), it is diagnosed that a short-circuit failure has occurred, and the process returns to the general flowchart of FIG. 3 to determine that there is a pin-to-pin failure (step 308). (Step 309).
[0036]
Here, as processing at the time of abnormality, appropriate processing such as sending out some alarm output or display output to the outside, interrupting the control, or transferring the control right to another microcomputer is performed.
[0037]
On the other hand, when the input logic of the port P1 does not change according to the output logic of the port P2 (steps 403LOW and 405HIGH), a diagnosis of normality is performed (step 409), and FIG. Returning to the general flow chart of FIG. 1, after determining that the port is normal (step 305), the mode of the port P2 is returned to the input mode again (step 306), and the process proceeds to the original normal control process (step 307). ).
[0038]
As described above, according to the diagnosis processing of the present invention described above, the function of one port P2 configured as the input / output port of the pair of ports P1 and P2 is switched from the input port to the output port. After that, a predetermined test signal is sent from one port P2 switched to the output port, the signal of the other port P1 in that state is read, and it is determined whether or not it changes according to the test signal In the case where a short-circuit failure (generally due to a short-circuit failure between pins) has occurred between the port P1 and the port P2, as indicated by a broken line 9 in FIG. This can be accurately diagnosed based on the determination result.
[0039]
In addition, in this embodiment, since a pulse train that is sufficiently shorter than the period of the signal normally obtained from the signal source symbolized by the switch 1 is used as the test signal, a normal signal is temporarily output during the diagnosis. Even if it is read from P1, it can be accurately distinguished from the changed signal. Therefore, this diagnosis process is not only performed in the initialization process immediately after the power is turned on, but also at an arbitrary time point during execution of the control program. The reliability of a short circuit failure between pins in this kind of one-chip microcomputer can be remarkably improved.
[0040]
In the circuit configuration shown in FIG. 1, the interface circuits IF1 and IF2 do not include the buffer circuit A. However, when the interface circuit IF having the buffer circuit A shown in FIG. As shown in FIG. 5B, a resistor R3 may be added to the output side of the buffer circuit A.
[0041]
【The invention's effect】
As described in detail above, according to the microcomputer device of the present invention, not only at the manufacturing stage in the factory, but also at any time after shipment, the short-circuit failure between adjacent terminal pins can be accurately diagnosed. It is possible to improve the reliability of this kind of one-chip microcomputer.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing a partial configuration of an internal circuit of a vehicle ECU to which the present invention is applied.
FIG. 2 is a circuit diagram showing a specific circuit configuration for realizing an input / output port.
FIG. 3 is a general flowchart schematically showing the contents of diagnostic processing according to the present invention.
FIG. 4 is a flowchart showing in detail a main part of a diagnostic process according to the present invention.
FIG. 5 is a waveform diagram showing signal states of ports P1 and P2 in the diagnostic processing according to the present invention.
FIG. 6 is a circuit diagram showing another example of an interface circuit.
[Explanation of symbols]
1 ECU circuit board 2 One-chip microcomputer 3 Internal bus 4 Input gate 5 Output latch 6 Port mode register 7 Mode switching gate 8 Tri-state buffer 9 Short circuit between ports IF1, IF2, IF Interface circuit SW1, SW2 Symbolic signal source Switch T1, T2 External input terminal R1, R2 Resistor C Capacitor D1, D2 Diode P1, P2 A pair of adjacent ports

Claims (3)

A first port in which a pair of adjacent ports are used as input ports, and an input / output port that can be arbitrarily switched between an input port and an output port via a program A microcomputer device configured by a second port, wherein the first port and the second port are electrically independent;
The microcomputer system program includes a diagnostic process for diagnosing a short-circuit failure between the pair of adjacent ports, and the diagnostic process uses the second port for output from the input port. Port function switching processing for switching to a port, test signal transmission processing for transmitting a predetermined test signal from the second port switched to the output port, and the first in a state where the test signal is transmitted A signal state determination process for reading a signal of a port and determining whether or not it changes in response to the test signal, A test signal is output from a port in which the second port is switched to an output port, and the period of the signal source input to the first port is such that the period of the test signal can be identified. A microcomputer device characterized in that the microcomputer device is set to be shorter . 2. The microcomputer apparatus according to claim 1, wherein the microcomputer apparatus is a one-chip microcomputer in which terminal pins corresponding to each port are arranged close to each other. 2. The microcomputer apparatus according to claim 1, wherein a predetermined abnormality process is executed in response to a diagnosis that a short circuit between a pair of adjacent ports is made in the diagnosis process.

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