JP6843543B2 - Microprocessors, methods of inspecting external circuits in microprocessors, and programs - Google Patents

Description

The present invention relates to a technique for self-inspecting the state of an external circuit connected to a bidirectional input / output port.

Patent Document 1 discloses a method for self-inspecting a passive component connected to a bidirectional input / output port (hereinafter, simply referred to as an input / output port). In the inspection method described in Patent Document 1, when a High / Low level is output from an output port, it is determined whether or not a phase change can be obtained at the input port according to the characteristics of an external circuit arranged between the two ports. To do.

Japanese Unexamined Patent Publication No. 2011-043440

The method described in Patent Document 1 can detect states other than GND shorts, but it is necessary to provide an input port and an output port separately, and both ports must be shorted outside the device at the time of inspection. However, it requires a complicated configuration. Therefore, an object of the present invention is to provide a microprocessor, an inspection method, and a program capable of inspecting the electrical characteristics and states of an external circuit connected to an input / output port with a simple configuration.

The microprocessor according to the present invention is a microprocessor having an input / output port and capable of inspecting an external circuit connected to the input / output port, and outputs a voltage of the input / output port that is outputting a specific level of voltage. After turning off, a monitoring means that monitors the voltage of the input / output port at regular intervals, an inspection means that inspects whether the voltage monitored by the monitoring means exceeds a predetermined threshold, and the input / output port. A calibration means for calibrating the inspection result obtained when the external circuit is connected to the input / output port by using the inspection result obtained when the external circuit is not connected to the input / output port. Based on the distribution of 1s and 0s in the data string calibrated by the calibration means, in addition to the electrical characteristics of the external circuit, at least the GND short, open, and the external circuit of the input / output port. It is characterized in that the presence / absence of connection is determined.

According to the present invention, it is possible to inspect the electrical characteristics and state of an external circuit connected to an input / output port of a microprocessor with a simple configuration.

It is a block diagram which shows an example of the hardware configuration of the microprocessor which concerns on 1st Embodiment of this invention. It is a figure which shows an example of the configuration of the input / output port shown in FIG. It is a figure which shows an example of the inspection voltage waveform. It is a figure which shows the inspection flow in 1st Example. It is a figure which shows an example of the circuit to be inspected. It is a figure for demonstrating the distribution of the number of detections when the inspection flow shown in FIG. 4 is executed with respect to a predetermined number of samples. It is a figure which shows the acquisition flow of the calibration value. It is a figure which shows the determination flow of the inspection result. It is a figure which shows an example of the printer unit of an inkjet printer. It is a block diagram which shows an example of the structure of a control board. It is a figure which shows an example of the control board to which a filter circuit is connected.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

[Example 1]
FIG. 1 is a block diagram showing an example of a hardware configuration of a microprocessor according to a first embodiment of the present invention. The microprocessor (MPU) 10 according to the first embodiment includes a CPU 104, a timer 105, a counter 106, an input / output port 107, and an input / output port 108. The MPU 10 further includes a memory 101 for storing the wait time described later, a memory 102 for storing the data string described later, and a memory 103 for storing the set value of the number of times the inspection voltage is read, which will be described later.

A resistor 110 and a capacitor 111 are connected to the input / output port 107 as a circuit to be inspected. The circuit to be inspected shown in FIG. 1 is an example, and other circuits to be inspected may be connected to the input / output port 107. On the other hand, nothing is connected to the input / output port 108. In this embodiment, the input / output port 108 is used to acquire the unique characteristics of the MPU 10, as will be described later. As will be described later, the MPU of this embodiment has an input / output port and can inspect an external circuit connected to the input / output port.

FIG. 2 is a diagram showing an example of the configuration of the input / output ports 107 and 108 shown in FIG. FIG. 2A shows the configuration of the input / output port 108. FIG. 2B shows the configuration of the input / output port 107. As shown in FIGS. 2A and 2B, the I / O ports 107 and 108 have the same configuration, and include an output buffer 201, an input buffer 202, and a pull-down resistor 203, respectively. The output buffer 201 has an output disable function and can control whether the output is on or off. In this embodiment, the output buffer 201 and the input buffer 202 are connected as shown in FIG. 2 to form an input / output buffer having both input and output functions. As described above, the resistor 110 and the capacitor 111 are connected to the input / output port 107, but nothing is connected to the input / output port 108.

Input / output ports 107 and 108 are highly versatile ports used as interfaces with peripheral devices. Although two input / output ports 107 and 108 are illustrated in FIG. 1, a large number of input / output ports are usually prepared in the MPU, and each input / output port is controlled by, for example, a motor driver IC. It outputs signals and reads voltage levels of sensors and switches.

FIG. 3 is a diagram showing an example of the inspection voltage waveform. Vp (t) indicates the time change of the voltage value of the voltage (hereinafter referred to as the inspection voltage) in the Vp line shown in FIG. t indicates the elapsed time.

First, at t ₀ , a high level voltage is output from the output buffer 201 shown in FIG. Therefore, Vp (t) at _{t 0 is 3.3V.} Note that 3.3V is an example, and other voltage values may be used. The high level voltage may be referred to as a specific level voltage.

Next, at t ₁ , the output (voltage output) of the output buffer 201 is disabled. Therefore, _{Vp (t) at t 1} gradually hangs down with the passage of time according to the time constant including the pull-down resistor 203 and the circuit to be inspected (resistor 110 and capacitor 111) shown in FIG.

The CPU 104 monitors Vp (t) after _{t 1.} Specifically, the CPU 104 repeatedly reads Vp (t) at regular intervals using the input buffer 202 shown in FIG. Then, the CPU 104 determines the pass / fail of the inspection based on the monitoring result.

Vth is a threshold value for determining whether the reading value of the input buffer 202 is 0 (Low level) or 1 (High level). In this embodiment, as shown in the lower figure of FIG. 3, the reading value of the input buffer 202 at each read timing is stored in the data string 301 as 0 or 1. The data string 301 is stored in the memory 102. t ₂ indicates the time when Vp (t) intersects this Vth.

In the example shown in FIG. 3, 1 is detected four times from t _{1 to t 2} as the reading value of the input buffer 202, and 0 is detected after _{t 2.} The CPU 104 determines the state of the circuit to be inspected by comparing the number of detections (here, 4) with the determination value. The determination value is experimentally obtained in advance and stored in the program ROM (not shown).

FIG. 4 is a diagram showing an inspection flow in the first embodiment. In this embodiment, the MPU 10 (specifically, the CPU 104) outputs a signal to the circuit to be inspected, and the MPU 10 detects a reaction peculiar to the circuit to be inspected to the signal output.

First, the MPU 10 initializes the read count N stored in the counter 106 to 1 (step S401).

Next, the MPU 10 outputs a high level voltage from the output buffer 201 (step S402). Then, the MPU 10 waits for a certain period of time until the voltage of the Vp line reaches the High level (here, 3.3 V) to disable (non-drive) the output buffer 201 (step S403).

Next, the MPU 10 waits using the timer 105 until a preset wait time elapses (step S404). In this embodiment, the information indicating the wait time is stored in the memory 101 in advance. Then, the MPU 10 reads the signal level at the present time t from the input buffer 202 (step S405). At this time, if Vp (t) exceeds the above threshold value, the MPU 10 determines that the signal level is 1 (High level). If Vp (t) is equal to or less than the above threshold value, the MPU 10 determines that the signal level is 0 (Low level). Then, the MPU 10 writes the reading value of the signal level to the Nth bit (the Nth bit counting from the least significant bit (LSB)) of the data string stored in the memory 102 (step S406).

Next, the MPU 10 determines whether or not the number of readings N has reached a predetermined set value (step S407). Information indicating the set value is stored in the memory 103 in advance. If the read count N has not reached the set value (No in step S407), the MPU 10 increments the read count N by 1 and returns to the process of step S404. If the number of readings N has reached the set value (Yes in step S407), the MPU 10 proceeds to the process of step S408.

Finally, the MPU 10 counts the number of bits in which 1 is continuously stored from the LSB (the leftmost end of 301 in FIG. 3) in the data string stored in the memory 102, and uses the number of bits as the inspection result. Acquire (step S408). As described above, in this embodiment, the number of readings performed until the reading value of the input buffer 202 is switched from 1 to 0 is acquired as the inspection result.

By executing the above processing, the MPU 10 of the present embodiment turns off the voltage output of the input / output port that is outputting the high level (specific level) voltage, and then sets the voltage of the input / output port at regular intervals. Monitor with. Then, the MPU 10 inspects whether or not the monitored voltage exceeds a predetermined threshold value (Vth). Therefore, the inspection voltage waveform and the data string 301 as shown in FIG. 3 are output, and the data acquisition for executing the inspection for the circuit to be inspected is completed.

FIG. 5 is a diagram showing an example of the circuit to be inspected. The configuration of the MPU 50 shown in FIG. 5 is the same as that of the MPU 10 shown in FIG. However, the MPU 50 has input / output ports 501 to 504. A circuit to be inspected including a resistor array (RA) 51 and a capacitor (array CA) 52 is connected to the MPU 50. Each input / output port of the MPU 50 is connected to a CR filter as shown in FIG. Specifically, the input / output port 501 is connected to the ground (GND) via the pins 1 and 8 of the RA51 and further via the Pin8 and Pin1 of the CA52. Input / output ports 502 to 504 are similarly connected to the GND. In RA51, resistors having the same resistance value are arranged between Pin1 and Pin8, between Pin2 and Pin7, between Pin3 and Pin6, and between Pin4 and Pin5, respectively. Similarly, in the CA52, a capacitor having the same capacitance is arranged between each pin.

Although the CR filter is taken as an example of the circuit to be inspected here, the circuit to be inspected may be any circuit as long as it has a time constant of a certain value or more.

In the inspection of the circuit to be inspected shown in FIG. 5, the processing shown in FIG. 4 is performed for each of the signals output from each input / output port of the MPU 50. That is, the MPU 50 outputs a high level voltage from the input / output port 501, and transmits a capacitor arranged between Pin 8 and Pin 1 of CA 52 via a resistor arranged between Pin 1 and Pin 8 of RA51. Charge. Next, the MPU 50 disables the output of the input / output port 501, which is outputting a high level voltage. Then, the discharge of the electric charge charged in the capacitor is started. At the same time, the MPU 50 starts reading the input / output port 501. The MPU 50 is read a plurality of times in a fixed cycle (for example, 128 times in a 1us cycle). The MPU 50 performs the same processing on the input / output ports 502 to 504.

It is assumed that the time constant τ of the circuit including the CR filter and the GND resistance (corresponding to the pull-down resistor 203 shown in FIG. 2) corresponding to the input / output port 501 is 25us. Further, it is assumed that the VIL at the input / output port 501 is Vcc × 36.8%. VIL is a voltage level that is perceived as the Low level. In this case, the voltage attenuation after the lapse of the time constant τ in the circuit including the CR filter and the GND resistance is 36.8%. Therefore, since 1 is detected during the 1st to 24th reads and 0 is detected during the 25th to 128th reads, the number of detections of 1 in the circuit including the CR filter and the GND resistance is 24. Hereinafter, the number of detections of 1 may be simply referred to as the number of detections.

On the other hand, the number of detections can vary greatly depending on the variation in the characteristics of each circuit element such as the VIL and leakage current of the input / output port, the resistance value of the CR filter, and the capacitance even when the circuit to be inspected is in a normal state. Therefore, it is necessary to set the judgment value of the inspection with a range in consideration of the variation in the number of detections due to this variation. However, when the range of the determination values reaches (overlaps) the number of detections that can be acquired when the circuit to be inspected is abnormal, it is necessary to perform the calibration process described later to cancel the variation. If there is no overlap, no calibration process is required. Therefore, in that case, the calibration value N0 can be set to zero for inspection in the process of FIG. 7 or FIG. 8 described later. Further, when there is no overlap, only the process of FIG. 8 may be executed without executing the process of FIG. 7. The above-mentioned determination value is experimentally obtained in advance and stored in a program ROM (not shown) or the like.

FIG. 6 is a diagram for explaining the distribution of the number of detections when the inspection flow shown in FIG. 4 is executed for a predetermined number of samples. FIG. 6A shows an example of the distribution of the number of detections when there is no overlap. As shown in FIG. 6A, when the circuits do not overlap, the distribution 611 when the circuit is normal and the distribution 612 when the circuit is abnormal do not intersect. Therefore, when there is no overlap, the normal value and the abnormal value are not mistaken for each other. On the other hand, FIG. 6B shows an example of the distribution of the number of detections in the case of overlapping. As shown in FIG. 6B, in the case of overlapping, the distribution 621 at the normal time and the distribution 622 at the abnormal time intersect. Therefore, it is impossible to distinguish between normal and abnormal in the area indicated by the diagonal line. In such a case, the calibration process described later reduces the variation on the MPU side such as the VIL of the input / output port and the leakage current fluctuation, and separates the normal and the abnormal. In FIG. 6C, the distribution image of the number of detections after calibration is shown by a broken line.

The calibration is performed to cancel the variation in the detection result due to the VIL and leakage current of the input / output port in the MPU or the individual difference in the stray capacitance of the MPU. Specifically, first, the processing shown in FIG. 4 is performed on an input / output port (referred to as a free port or an unused input / output port) to which no circuit is connected, and the inspection result of the free port is acquired. Will be done. Next, the processing shown in FIG. 4 is performed on the input / output port (referred to as the inspection target port) to which the circuit to be inspected is connected, and the inspection result of the inspection target port is acquired. Then, the inspection result of the free port is subtracted from the inspection result of the inspection target port. By doing so, it is possible to cancel the variation in the inspection result due to the individual difference of the MPU, and it is possible to obtain the inspection result in which the state of the circuit to be inspected is purely reflected.

Here, the calibration process and the inspection result determination process in this embodiment will be specifically described with reference to FIGS. 7 and 8. FIG. 7 is a diagram showing a flow for acquiring calibration values. FIG. 8 is a diagram showing a determination flow of inspection results.

First, the MPU 10 performs the process shown in FIG. 4 on the unused input / output port (for example, the input / output port 108 shown in FIG. 1) (step S701). Then, the MPU 10 substitutes the inspection result acquired in the process of step S408 into the calibration value N0 (step S702).

Next, the MPU 10 performs the process shown in FIG. 4 on the inspection target port (for example, the input / output port 107 shown in FIG. 1) (step S801). Then, the MPU 10 substitutes the inspection result acquired in the process of step S408 into the pre-calibration inspection result N1 (step S802). The MPU 10 subtracts the calibration value N0 acquired in step S702 from the pre-calibration inspection result N1 and substitutes the result into the post-calibration inspection result N1'(step S803). If there is no overlap described above, the process of step S803 may be skipped and the value of N1 may be treated as N1'as it is. The MPU 10 compares the post-calibration inspection result N1'with the determination value (step S804). The number of bits in which 1 is stored may be acquired as an inspection result, and the process of step S804 may be executed based on the inspection result and the determination value indicating the number of bits. In addition, the elapsed time calculated from the number of bits in which 1 is stored (that is, the elapsed time until the voltage value falls below the threshold value) is acquired as the inspection result, and the processing of S804 is performed based on the elapsed time and the determination value. May be executed. When the inspection result N1'after calibration is within the range of the determination value (Yes in step S804), the MPU 10 determines that the inspection result is normal (OK), that is, there is no abnormality in the circuit to be inspected (step S805). ). Further, when the inspection result N1'after calibration is out of the range of the determination value (No in step S804), the MPU 10 determines that the inspection result is abnormal (NG), that is, the circuit to be inspected has an abnormality (No). Step S806). Normally, the number of detections (N1) of the port to be inspected connected to the circuit to be inspected with a capacitor is larger than the number of detections (N0) of an unused input / output port to which the circuit to be inspected with a capacitor is not connected. Based on this characteristic, a determination value such as 1 or more may be set as an example of the range of the determination values. As described above, by making a judgment using the inspection result after calibration, even if the distribution of the number of detections overlaps as shown in FIG. 6B, the electricity of the circuit to be inspected (external circuit) It is possible to appropriately judge whether or not the target characteristic (here, the time constant) is normal. In other words, it can be determined that a normal circuit to be inspected (external circuit) is connected to the port to be inspected. If the test result can be obtained correctly even if the individual difference of MPU is taken into consideration, calibration is not necessary.

In this embodiment, it is assumed that the inspection voltage waveform is attenuated while drawing a quadratic curve. Then, the number of bits in which 1 is continuously stored from the LSB in the data string stored in the memory 102 is used as a determination criterion. However, the entire area of the data string stored in the memory 102 may be used as a determination criterion. For example, the distribution of values over the entire data string may be used as a criterion. According to such a form, it is possible to determine the GND short or open of the input / output port. For example, when the entire area of the data string is 0, it may be determined that the input / output ports are GND shorted. Further, for example, when the value fluctuates over the entire data string, it may be determined that the input / output port is open. In addition, the presence or absence of individual components constituting the external circuit at the end of the input / output port may be inspected.

In addition, the inspection of the mounting board is often performed by a dedicated inspection device. In the case where the inspection device is used in this way, it is necessary to provide contacts with the inspection device in all the circuit blocks. Therefore, it is necessary to provide tens to hundreds of contacts on the substrate, which hinders further increase in density. In addition, there is a fundamental problem that poor contact between the probe and the contact may occur due to deterioration of the probe, adhesion of dust, flux, and the like. In this embodiment, since a dedicated inspection device is not used, such a contact is not required. As a result, it becomes possible to realize a higher density of the mounting substrate. Moreover, since no contact is required, it is not necessary to consider problems such as poor contact with the probe.

Next, an example when this embodiment is applied to a printer will be shown. FIG. 9 is a diagram showing an example of a printer unit of an inkjet printer. The printer unit shown in FIG. 9 includes a transport mechanism 901, a cleaning mechanism 902, a chassis 903, a carriage 904, an automatic transport mechanism 905, a control board 906, and a flat cable 907. The transport mechanism 901 transports the recording medium. The cleaning mechanism 902 cleans the nozzles of the print head. Carriage 904 carries the printhead. The automatic transfer mechanism 905 takes out only the uppermost sheet from the plurality of recording media and feeds it to the print unit. The flat cable 907 is a cable for transmitting a printhead control signal output from the control board 906 to the printhead.

FIG. 10 is a block diagram showing an example of the configuration of the control board 906. The MPU 1001 has the configuration shown in FIG. The MPU 1001 controls the entire device based on the program stored in the ROM 1004. The printhead receives the printhead control signal generated by the MPU 1001 via the flat cable 907. Then, the print head 1002 ejects ink droplets to the recording medium based on the received print head control signal.

The printhead control signal is a high-speed signal of several MHz. The flat cable 907 that transmits the printhead control signal usually has a length of about 1 m. Therefore, it is necessary to insert a filter circuit on the control board 906 side in order to form a waveform and reduce the radiated electromagnetic field.

FIG. 11 is a diagram showing an example of a control board 906 to which a filter circuit is connected. For the filter circuit, for example, a delay circuit is used to suppress ringing of the waveform due to the inductor component of the flat cable and to cancel unnecessary harmonic components. A typical example is a CR filter. RA1102-1104 is the same as RA51 shown in FIG. CA1105-1107 is similar to CA52 shown in FIG. The connector 1108 is a connector for connecting the flat cable 907 to the print head 1002. In the example shown in FIG. 11, CR filter circuits are inserted in all 12 signal lines for transmitting the head control signal. Further, in the example shown in FIG. 11, the MPU 1001 executes the process shown in FIG. 8 to perform an inspection on each signal line. At that time, the MPU 1001 acquires the calibration value N0 in advance by executing the process shown in FIG. 7 on the unused input / output ports (not shown).

As described above, according to the present embodiment, the state and electrical characteristics of the CR filter circuit can be inspected with a simple configuration without providing the above-mentioned contacts in each signal line. Therefore, this embodiment is suitable for mounting tests of CR filter circuits and the like.

In the present embodiment, it has been described that the MPU 10 executes all the processes shown in FIG. 8, but for example, another determination device may execute the processes after step S803.

(Other embodiments)
The present invention supplies a program that realizes one or more functions of the above embodiment to a system or device via a network or storage medium, and one or more processors in the computer of the system or device reads and executes the program. It can also be realized by processing. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

Claims (11)

A microprocessor that has an input / output port and can inspect external circuits connected to the input / output port.
A monitoring means that monitors the voltage of the input / output port at regular intervals after turning off the voltage output of the input / output port that is outputting a specific level of voltage.
An inspection means for inspecting whether or not the voltage monitored by the monitoring means exceeds a predetermined threshold value, and
Calibration that calibrates the inspection result obtained when the external circuit is connected to the input / output port by using the inspection result obtained when the external circuit is not connected to the input / output port as a calibration value. Means and
Have,
Based on the distribution of 1s and 0s in the data string calibrated by the calibration means, in addition to the electrical characteristics of the external circuit, at least the GND short, open, and the presence or absence of the connection of the external circuit of the input / output port. A microprocessor characterized by being determined. The inspection means obtains the elapsed time until the voltage value obtained by monitoring the voltage of the input / output port at regular intervals becomes equal to or less than the predetermined threshold value as the inspection result.
It is characterized in that it is determined whether or not the predetermined external circuit is connected based on the elapsed time which is the inspection result.
The microprocessor according to claim 1. The inspection means
For each of the voltage values obtained by monitoring the voltage of the input / output port at regular intervals, it is determined whether or not the voltage value exceeds the predetermined threshold value, and when the voltage value exceeds the predetermined threshold value. Stores 1 in order from the least significant bit of the data string as the inspection result when it is equal to or less than the predetermined threshold value.
It is characterized in that it is determined whether or not the predetermined external circuit is connected based on the value of the data string.
The microprocessor according to claim 1. The inspection means
In the data string, when the number of 1s continuously stored from the LSB is within the range of the predetermined determination value, it is determined that the predetermined external circuit is connected to the input / output port.
The microprocessor according to claim 3. The external circuit is a CR filter circuit.
The electrical characteristics of the external circuit are determined and
The electrical properties include at least a time constant
The microprocessor according to any one of claims 1 to 4. An inspection method for inspecting an external circuit connected to an input / output port in a microprocessor having an input / output port.
After turning off the voltage output of the input / output port that is outputting a specific level of voltage, the step of monitoring the voltage of the input / output port at regular intervals and
An inspection step for inspecting whether the monitored voltage exceeds a predetermined threshold, and
Calibration that calibrates the inspection result obtained when the external circuit is connected to the input / output port by using the inspection result obtained when the external circuit is not connected to the input / output port as a calibration value. Steps and
Have,
Based on the distribution of 1s and 0s in the data string calibrated in the calibration step, in addition to the electrical characteristics of the external circuit, at least the GND short, open, and the presence or absence of the external circuit connection of the input / output port. An inspection method characterized in that is determined. In the inspection step, the elapsed time until the voltage value obtained by monitoring the voltage of the input / output port at regular intervals becomes equal to or less than the predetermined threshold value is acquired as the inspection result.
It is characterized in that it is determined whether or not the predetermined external circuit is connected based on the elapsed time which is the inspection result.
The inspection method according to claim 6. In the inspection step
For each of the voltage values obtained by monitoring the voltage of the input / output port at regular intervals, it is determined whether or not the voltage value exceeds the predetermined threshold value, and when the voltage value exceeds the predetermined threshold value. Stores 1 in order from the least significant bit of the data string as the inspection result when it is equal to or less than the predetermined threshold value.
It is characterized in that it is determined whether or not the predetermined external circuit is connected based on the value of the data string.
The inspection method according to claim 6. In the inspection step
In the data string, when the number of 1s continuously stored from the LSB is within the range of the predetermined determination value, it is determined that the predetermined external circuit is connected to the input / output port.
The inspection method according to claim 8. The external circuit is a CR filter circuit.
The electrical characteristics of the external circuit are determined and
The electrical properties include at least a time constant
The inspection method according to any one of claims 6 to 9. A program for operating a computer as a microprocessor according to any one of claims 1 to 5.

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