Patent ID: 12196822

DESCRIPTION OF EMBODIMENTS

First Embodiment

FIG.1is a circuit configuration diagram of the physical quantity measuring device10according to the first embodiment of the present invention. The physical quantity measuring device10includes a large scale integration (LSI)1and a humidity sensor2. The LSI1(second semiconductor integrated circuit) receives, from the humidity sensor2, a signal indicating a physical quantity (flow rate of fluid) measured by the humidity sensor2(first semiconductor integrated circuit), analyzes the signal, and outputs data indicating the physical quantity.

The LSI1and the humidity sensor2are connected by a power source line VDD, a reset signal line nRST, a data signal line SDA, a synchronization signal line SCL, and a ground line GND (these wirings correspond to “a plurality of signal lines”).

The power source line VDD supplies power from a power source circuit11to the humidity sensor2. The ground line GND connects the LSI1and the humidity sensor2to a reference potential (ground potential). The data signal line SDA is a signal line for data transmission and reception in inter-integrated circuit (I2C) communication. The synchronization signal line SCL is a signal line for a synchronization signal in I2C communication.

The LSI1includes the power source circuit11, the control circuit12, a test terminal TEST, and the power source terminal VCC. The control circuit12transmits a command signal and a reset signal to the humidity sensor2. The test terminal TEST will be described later.

The humidity sensor2includes the load circuit21. The load circuit21is arranged so as to connect between the power source line VDD and the reset signal line nRST. This causes the reset signal line nRST to be pulled up by power source voltage. Therefore, the control circuit12sets nRST to a high level when operating the humidity sensor2in the normal state, and sets nRST to a low level when causing the humidity sensor2to transition to the reset state. This allows the control circuit12to transmit a reset signal to the humidity sensor2.

The control circuit12transmits a command to the humidity sensor2via the data signal line SDA. When the humidity sensor2is operating normally, the humidity sensor2returns a response signal via the data signal line SDA. When the response signal is not returned due to some error or the like in the humidity sensor2(or when the humidity sensor2returns an error), the control circuit12transmits a reset signal to the humidity sensor2via the reset signal line nRST. If the reset signal line nRST is not disconnected, the humidity sensor2transitions to the reset state, and if the reset signal line nRST is disconnected, the humidity sensor2continues to operate. Therefore, the control circuit12can diagnose whether or not the reset signal line nRST is disconnected based on whether or not the humidity sensor2continues to operate by transmitting the reset signal.

However, in the inspection process of the physical quantity measuring device10, since the humidity sensor2is considered to operate normally, the humidity sensor2always returns a response signal. Then, in the inspection process, since the control circuit12does not have an opportunity to transmit the reset signal to the humidity sensor2, it is not possible to diagnose disconnection of the reset signal line nRST using the reset signal. Therefore, in the first embodiment, the control circuit12includes a means for transmitting a reset signal to the humidity sensor2regardless of whether or not a response signal is returned from the humidity sensor2.

As a specific example, the control circuit12may transmit a reset signal to the humidity sensor2regardless of how the humidity sensor2operates with respect to the command transmitted to the humidity sensor2. For example, the control circuit12is notified that the inspection process is being performed by some method, and upon receiving the notification, the control circuit12transmits a reset signal to the humidity sensor2. This makes it possible to diagnose disconnection of the reset signal line nRST even when the humidity sensor2is operating normally.

FIG.2is a view illustrating another configuration example of the physical quantity measuring device10. InFIG.2, the physical quantity measuring device10includes a flow rate sensor3, in addition to the humidity sensor2, as physical quantity sensors. In addition to the LSI1, an AD converter16, a logic circuit13, an output circuit14, and an oscillator15are included.

The flow rate sensor3outputs, by signals QH and QL, a result of measuring the humidity. The AD converter16receives the signals QH and QL, converts them into digital signals, and outputs them to the logic circuit13. Difference voltage between the signal QH and the signal QL is a signal indicating a change in the flow rate. Since the flow rate sensor3does not include a circuit for executing a command from the control circuit12, it is not necessary to reset the flow rate sensor3. Therefore, inFIG.2, the flow rate sensor3is not connected to the reset signal line nRST. In a case of connecting a sensor that needs to be reset, it is only required to connect the reset signal line nRST similarly to the humidity sensor2.

The logic circuit13controls the control circuit12. The logic circuit13receives the measurement result of the humidity sensor2via the control circuit12and receives the measurement result of the flow rate sensor3via the AD converter16. The logic circuit13outputs each measurement result via the output circuit14. The oscillator15provides a clock signal to the logic circuit13.

Similarly to the operation described with reference toFIG.1, the logic circuit13and the LSI1can transmit a reset signal to the humidity sensor2regardless of whether or not the humidity sensor2responds to the command.

Second Embodiment

FIG.3is a view describing the configuration of the physical quantity measuring device10according to the second embodiment of the present invention. In the second embodiment, the control circuit12includes a first control circuit12a, a second control circuit12b, and an AND circuit12c. Other configurations are similar to those of the first embodiment.

The first control circuit12atransmits a command to the humidity sensor2similarly to the first embodiment. When the humidity sensor2does not respond to the command or does not perform the operation designated by the command, the first control circuit12atransmits a reset signal to the humidity sensor2. That is, the first control circuit12acontrols the humidity sensor2in response to the response from the humidity sensor2.

The second control circuit12btransmits a reset signal to the humidity sensor2in accordance with a signal input to the test terminal TEST. That is, the second control circuit12bcontrols the humidity sensor2regardless of the response from the humidity sensor2.

The AND circuit12caggregates the signal output from the first control circuit12ato the reset signal line nRST and the signal output from the second control circuit12bto the reset signal line nRST, and outputs a logical product of them to the reset signal line nRST. Therefore, what is finally output to the reset signal line nRST is the output of the AND circuit12c.

FIG.4is a flowchart illustrating operation of the control circuit12in the second embodiment. When a low level signal is input to the test terminal TEST (S401: Low), the second control circuit12boutputs low level to the signal line nRST_2. Therefore, since the output of the AND circuit12calso becomes the low level, the reset signal line nRST also becomes the low level (reset instruction) (S404).

When a high level signal is input to the test terminal TEST (S401: High), the second control circuit12boutputs high level to the signal line nRST_2.

When the humidity sensor2responds to the command, the first control circuit12aoutputs high level to the signal line nRST_1(S402: High). In this case, since the output of the AND circuit12cbecomes the high level, the reset signal line nRST becomes the high level (normal operation) (S403).

When the humidity sensor2does not respond to the command, the first control circuit12aoutputs the low level to the signal line nRST_1(S402: Low). In this case, since the output of the AND circuit12cbecomes the low level, the reset signal line nRST becomes the low level (reset instruction) (S404).

When a low level signal is input to the test terminal TEST (S401: Low), the second control circuit12boutputs low level to the signal line nRST_2. In this case, since the output of the AND circuit12cbecomes the low level, the reset signal line nRST becomes the low level (reset instruction) (S404).

According to the above operation, when the high level is input to the test terminal TEST, the reset signal is controlled according to whether or not the first control circuit12areceives a response from the humidity sensor2. On the other hand, when the low level is input to the test terminal TEST, a reset signal is transmitted to the humidity sensor2regardless of whether or not a response is received from the humidity sensor2. Therefore, when performing the inspection process, it is only required to input the low level the test terminal TEST.

In the second embodiment, the AND circuit12conly needs to output the logical product of outputs from the first control circuit12aand the second control circuit12b, and thus does not necessarily need to be configured by the AND circuit itself. In other words, as long as the logical product of these outputs can be finally output to the reset signal line nRST, the AND circuit12cmay be replaced by an arbitrary logic circuit.

Third Embodiment

FIG.5is a configuration diagram of the physical quantity measuring device10according to the third embodiment of the present invention. In the third embodiment, the physical quantity measuring device10includes two humidity sensors2. Each of the humidity sensors2communicates with the LSI1using an I2C protocol. Each of the humidity sensors2is connected in parallel to the LSI1, and the LSI1transmits the same command (including a reset signal) to each of the humidity sensors2. Therefore, the LSI1transmits the reset signal to all the humidity sensors2. Other configurations are the same as those in the first and second embodiments.

According to the configuration illustrated inFIG.5, (a) when any of the humidity sensors2does not respond to the command, the LSI1transmits a reset signal to all the humidity sensors2, and (b) when the inspection process is performed, the LSI1transmits a reset signal to all the humidity sensors2. The same applies when there are three or more humidity sensors2. This makes it possible to achieve the same operation as in the first and second embodiments even in a case of including a plurality of humidity sensors2.

In a case of individually transmitting a command to each of the humidity sensors2, for example, it is only required to separately provide a chip select signal line or the like, and transmit the command after selecting in advance any of the humidity sensors2. The humidity sensor2responds to the command only when the humidity sensor2is selected in advance. However, regarding the reset signal, all the humidity sensors2may perform the same operation (that is, reset) regardless of whether or not being selected.

FIG.6is a view illustrating another configuration example of the physical quantity measuring device10according to the third embodiment. InFIG.6, the first humidity sensor2and the LSI1communicate with each other by an I2C protocol, and the second humidity sensor2and the LSI1communicate with each other by a serial peripheral interface (SPI) protocol. Specifically, the second humidity sensor2uses four signals of a master input slave input (MOSI), a master input slave output (MISO), a clock (SCLK), and a chip select (CS).

Also in the configuration illustrated inFIG.6, the LSI1operates similarly toFIG.5. However, the command for the second humidity sensor2conforms to the SPI protocol. This makes it possible to achieve the same operation as in the first and second embodiments even in a case where the plurality of humidity sensors2communicate with each other using different communication protocols.

Fourth Embodiment

FIG.7is a view describing the configuration of the physical quantity measuring device10according to the fourth embodiment of the present invention. In the fourth embodiment, the second control circuit12bis connected to a memory12din place of the test terminal TEST. Since other configurations are similar to those of the second embodiment, differences from the second embodiment will be mainly described below.

The second control circuit12breceives an instruction value from a specific storage area of the memory12din place of input from the test terminal TEST. The second control circuit12boutputs low level if the instruction value is a value instructing to output the reset signal, and outputs high level if the instruction value is a value instructing the normal operation. The subsequent operation is the same as that of the second embodiment.

The instruction value stored in the memory12dmay be stored in the logic circuit13, for example, or may be input from an external terminal such as the test terminal TEST. The instruction value may be notified to the logic circuit13or the control circuit12by other appropriate means, and the logic circuit13or the control circuit12may store the instruction value into the memory12d.

In the fourth embodiment, the second control circuit12bmay use the test terminal TEST in combination. For example, the low level may be output when at least any of the instruction value stored in the memory12dand the input from the test terminal TEST is the low level or a value corresponding thereto.

In the fourth embodiment, even without the test terminal TEST, the control circuit12can determine by itself whether or not to output the reset signal. Therefore, for example, by configuring the memory12das a part of the LSI1and storing the instruction value, the physical quantity measuring device10can diagnose disconnection of the reset signal line in a stand-alone manner.

Fifth Embodiment

FIG.8is a configuration diagram of the physical quantity measuring device10according to the fifth embodiment of the present invention. In the fifth embodiment, the load circuit21is arranged so as to connect between the ground line GND and the reset signal line nRST. Due to this, the reset signal line nRST is pulled down by the ground voltage. Therefore, the control circuit12sets nRST to the low level when operating the humidity sensor2in the normal state, and sets nRST to the high level when causing the humidity sensor2to transition to the reset state. This allows the control circuit12to transmit a reset signal to the humidity sensor2. Other configurations are similar to those of the first to fourth embodiments.

Even in a case where the load circuit21included in the humidity sensor2is pulled down as in the fifth embodiment, the LSI1can transmit, similarly to the first to fourth embodiments, the reset signal regardless of whether or not the humidity sensor2responds. It is therefore possible to achieve the same operation similarly to the first to fourth embodiments.

Sixth Embodiment

FIG.9Ais a view illustrating the configuration example of the load circuit21. The load circuit21can be configured by, for example, a resistive element as in the left inFIG.9A, or can be configured by a switching element as in the right inFIG.9A. Other configurations are the same as those in the first to fifth embodiments.

FIG.9Bis a view illustrating the configuration example of the load circuit21. Even in the configuration in which the load circuit21is pulled down as in the fifth embodiment, the load circuit21can be configured by a resistive element or a switching element. Other configurations are the same as those in the first to fifth embodiments.

Modifications of Present Invention

The present invention is not limited to the above-described embodiments, and includes various modifications. For example, the above-described embodiments have been described in detail in order to describe the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the described configurations. It is also possible to replace a part of the configuration of a certain embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of the certain embodiment. Another configuration can be added to, deleted from, or replaced with a part of the configuration of each embodiment.

In the above-described embodiments, the circuit elements of the LSI1and the humidity sensor2may be integrated into one integrated circuit or the like. Similarly, circuit elements of the other sensors may be integrated with the LSI1.

In the above-described embodiments, it has been described that the control circuit12can transmit the reset signal to the humidity sensor2regardless of whether or not the humidity sensor2responds. The signal that can be transmitted regardless of a response from the sensor is not limited to the reset signal, and other signals may be transmitted. That is, the method according to the present invention can be applied in a case where a signal configured to be transmitted only when a specific condition is satisfied is needed to transmit regardless of whether or not the condition is satisfied.

In the above-described embodiments, a configuration example of the physical quantity measuring device10including the LSI1and the sensors has been described, but the present invention is not limited to this. That is, the present invention can be applied to other semiconductor devices that transmit commands from the first semiconductor circuit to the second semiconductor circuit.

In the above-described embodiments, the control circuit12and the logic circuit13can be configured by hardware such as a circuit device in which these functions are implemented, or can be configured by an arithmetic device such as a central processing unit (CPU) executing software in which these functions are implemented. In the present embodiment, the communication method has been described with examples of I2C and SPI, but the present invention can also be applied to a communication protocol for performing communication confirmation such as controller area network (CAN) communication.

REFERENCE SIGNS LIST

1LSI2humidity sensor3flow rate sensor10physical quantity measuring device11power source circuit12control circuit12afirst control circuit12bsecond control circuit12cAND circuit12dmemory21load circuit