This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2022-183122, filed on Nov. 16, 2022, the entire contents of which are incorporated herein by reference.
The present disclosure relates to a semiconductor device and a communication system.
A semiconductor device provided with a serial communication function has been used in various applications.
An example of a circuit technique related to serial communication is known in the art.
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the present disclosure.
Reference will now be made in detail to various embodiments, examples of which are illustrated in the accompanying drawings. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it will be apparent to one of ordinary skill in the art that the present disclosure may be practiced without these specific details. In other instances, well-known methods, procedures, systems, and components have not been described in detail so as not to unnecessarily obscure aspects of the various embodiments.
Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the drawings.
Communication by a UART (Universal Asynchronous Receiver/Transmitter) is performed between the MCU 2 and the CAN transceiver 3. The UART is a protocol for exchanging serial data between two devices. In the UART, bidirectional communication is performed between a transmitting side and a receiving side by two lines.
Communication by the CAN bus 4 is performed between the CAN transceivers 3 and 5. The CAN transceiver 3 includes a TXD (transmission data input) terminal 3A and an RXD (reception data output) terminal 3B. The CAN transceiver 3 outputs the data inputted to the TXD terminal 3A to the CAN bus 4, and outputs the data inputted from the CAN bus 4 from the RXD terminal 3B.
The CAN transceiver 5 includes an RXD terminal 5A and a TXD terminal 5B. The CAN transceiver 5 outputs the data inputted to the TXD terminal 5B to the CAN bus 4, and outputs the data inputted from the CAN bus 4 from the RXD terminal 5A.
The semiconductor device 1 is an IC (integrated circuit) in which a circuit having a predetermined function is integrated, and is configured, for example, as an LED (light emitting diode) driver IC. Further, the n semiconductor devices 1 do not all have the same function.
The semiconductor device 1 includes an RX (reception data input) terminal TA and a TX (transmission data output) terminal 1B. An n number of RX terminals TA are commonly connected to the RXD terminal 5A. An n number of TX terminals 1B are commonly connected to the TXD terminal 5B.
Since the n semiconductor devices 1 respond to the same protocol, the n semiconductor devices 1 can be commonly connected to the same CAN transceiver 5. Reception data RX outputted from the RXD terminal 5A is inputted to the n RX terminals 1A. The device address of one of the n semiconductor devices 1 is specified in the reception data RX. Furthermore, the transmission data TX outputted from the TX terminal 1B is inputted to the TXD terminal 5B.
The MCU 2 and the CAN transceiver 3 are installed at the substrate 6. The n semiconductor devices 1 and the CAN transceiver 5 are installed at a substrate 7 different from the substrate 6. The substrate 6 and the substrate 7 are connected by a harness (not shown). The CAN bus 4 is installed by the harness.
The n RX terminals 1A are commonly connected to the RXD terminal 2A of the MCU 2. The n TX terminals 1B are commonly connected to the TXD terminal 2B of the MCU 2.
The CANH terminal and the CANL terminal are respectively connected to each line of the CAN bus 4. Terminating resistors R1 and R2 are connected in series between the CANH terminal and the CANL terminal. The resistance values of the terminating resistors are determined by ISO11898, and each of the terminating resistors R1 and R2 is composed of a 60Ω resistor. One end of a capacitor C1 is connected to a connection node N1 to which the resistors R1 and R2 are connected.
The driver 92 includes a PMOS transistor (P-channel MOSFET (metal-oxide-semiconductor field-effect transistor)) 92A, a diode 92B, an NMOS transistor (N-channel MOSFET) 92C, and a diode 92D. The source of the PMOS transistor 92A is connected to an application terminal of a power supply voltage VCC. The drain of the PMOS transistor 92A is connected to the anode of the diode 92B. The cathode of the diode 92B is connected to the CANH terminal. The source of the NMOS transistor 92C is connected to the ground end. The drain of the NMOS transistor 92C is connected to the cathode of the diode 92D. The anode of the diode 92D is connected to the CANL terminal. The diodes 92B and 92D are used to prevent backflow of a current when a surge occurs.
The driver controller 91 controls the on/off of the PMOS transistor 92A and the NMOS transistor 92C based on the transmission data TX inputted from the outside via the TXD terminal.
More specifically, since when the PMOS transistor 92A and the NMOS transistor 92C are turned on, the current flowing through the terminating resistors R1 and R2 is common, the voltage drops occurring in the terminating resistors R1 and R2 are the same, the high-side signal CANH generated at the CANH terminal is a voltage higher than the voltage at a connection node N1 (=midpoint voltage) by the voltage drop, and the low-side signal CANL generated at the CANL terminal is a voltage lower than the voltage at the connection node N1 (=midpoint voltage) by the voltage drop. In this case, the high-side signal CANH is at a high level, and the low-side signal CANL is at a low level.
Here, the CANH terminal and the CANL terminal are connected to an application terminal of a power supply voltage VCC2 via resistors R91 and R92, respectively. When the PMOS transistor 92A and the NMOS transistor 92C are turned off, the voltage at the connection node N1 is gradually brought closer to the second power supply voltage VCC2 due to the action of the resistors R91 and R92, which have relatively high resistance values. The second power supply voltage VCC2 is the low level of the high-side signal CANH and the high level of the low-side signal CANL, and is the same voltage as the midpoint voltage.
In this way, the transmission data TX inputted to the TXD terminal is outputted from the CANH terminal and the CANL terminal to the CAN bus 4.
Meanwhile, the output part 94 includes a PMOS transistor 94A and an NMOS transistor 94B. The source of the PMOS transistor 94A is connected to the application terminal of the power supply voltage VCC. The drain of the PMOS transistor 94A is connected to the drain of the NMOS transistor 94B at anode N92. The source of the NMOS transistor 94B is connected to the ground end. The voltage at the CANH terminal and the voltage at the CANL terminal are inputted to the receiver 93. The output terminal of the receiver 93 is connected to a node N91 to which the gate of the PMOS transistor 94A and the gate of the NMOS transistor 94B are connected. The node N92 is connected to the RXD terminal.
The receiver 93 applies a signal of a high level or a low level to the node N91 depending on a difference in input voltages. Therefore, the output part 94 outputs a signal, in which the output of the receiver 93 is logically inverted, to the outside as reception data RX from the RXD terminal. In this way, the data inputted from the CAN bus 4 is outputted from the RXD terminal.
Prior to describing the embodiments of the present disclosure, a comparative example for comparison will be described. This will make problems clearer.
The communication part 11 receives reception data RX via the RX terminal TA. The communication part 11 outputs transmission data TX via the TX terminal 1B. The communication part 11 includes a register 11A for storing data. Furthermore, the communication part 11 includes a counter 11B that counts a clock CLK for transition control of an internal state.
Here, the data configuration of the reception data RX will be described by using the timing chart shown in
In the UART, communication is performed by data units called frames. A frame is composed of bit data from a start bit to a stop bit. The start bit is at a low level and the stop bit is at a high level. Bit data having a predetermined number of bits is arranged between the start bit and the stop bit. For example, if the predetermined number of bits is 8 bits, the frame is composed of bit data of 10 bits.
As shown in
The synchronization frame SYN is bit data for setting a baud rate in the semiconductor device 1. The baud rate is an index value indicating how many times digital data can be modulated in one second. For example, in serial communication in which one bit of digital data is transmitted by one modulation, the baud rate can be understood as an index value of communication speed (unit: bps [bit per second]).
The device frame DV includes a device address, a Read/Write bit, and the like. The device address is bit data indicating the address of a target device (semiconductor device 1). The Read/Write bit is bit data indicating Read or Write. Read indicates data reading from the semiconductor device 1 (Read process), and Write indicates data writing on the semiconductor device 1 (Write process).
The data number frame ND is bit data indicating the number of frames of the data frame DT. The register address frame AD is bit data indicating an address in the register 11A. The data frame DT is bit data indicating a data body transmitted by the reception data RX. The CRC frames CRL and CRH are bit data indicating an error detection code added to the data frame DT.
In
As shown in
In this case, after receiving the reception data RX, the communication part 11 of Device 1 outputs the transmission data TX from the TX terminal 1B as Read back. The communication part 11 outputs the transmission data TX by using the data read from the register 11A as a read data frame RDT. When transmitting a plurality of read data frames RDT as shown in
At this time, the communication part 11 of Device 1 makes transition of the internal state in accordance with the transmission timing of the transmission data TX. Further, in
On the other hand, in the communication part 11 of Device 2 other than the target device, after receiving the reception data RX, transition control of the internal state is performed based on the count of the clock CLK by the counter 11B. The transition control is performed based on the baud rate (bps) and a frequency of the clock CLK. The clock CLK of Device 2 is asynchronous with the clock CLK of Device 1, and transition control of the internal state is performed in Device 2 at its own timing. Further, in
In
In this case, the following problems arise. In
In the communication part 11 of Device 2, transition control of the internal state is performed based on the count of the clock CLK by the counter 11B but there is a possibility that a deviation in the timing of transition to the idle state may occur due to sampling errors. The larger the number of frames to be processed, the more sampling errors will accumulate and the timing deviation will become larger.
However,
For example, in the case of a sampling error where there is a one clock deviation in 8 bits, the error will be 12.5 clocks in 10 frames (10 bits×10). If an upper limit of an allowable deviation is 32 clocks, then a malfunction may occur in 26 frames since 32 clocks×8 bits=256 bits.
As described above, in order to solve the problem of malfunctions caused by Read back when the semiconductor device 1 is connected to the CAN transceiver 5, various embodiments described below are implemented.
In this embodiment, when Device 1, which is the target device, outputs transmission data TX as Read back, the communication part 11 of Device 2, which is other than the target device, performs the following operation. In this case, the synchronization part 11C monitors the transmission data TX and upon detecting a stop bit and a start bit at the frame switching in the transmission data TX, the synchronization part 11C resets the count of the clock CLK by the counter 11B (see the arrows in
Further, even in the case of the communication system 102 (see
In this embodiment, when Device 1, which is the target device, outputs transmission data TX as Read back, the communication part 11 of Device 2, which is other than the target device, performs the following operation. In this case, the synchronization part 11C monitors the reception data RX and upon detecting a stop bit and a start bit at the frame switching in the reception data RX, the synchronization part 11C resets the count of the clock CLK by the counter 11B (see the arrows in
However, in the case of the communication system 102 (see
In this embodiment, when Device 1, which is a target device, outputs transmission data TX as Read back, the transmission data TX is inputted to the reception data RX. At this time, the communication part 11 of Device 2, which is not the target device, performs the following operation. In this case, the synchronization part 11C monitors the reception data RX and upon detecting a stop bit and a start bit at the frame switching in the reception data RX, the synchronization part 11C resets the count of the clock CLK by the counter 11B (see the arrows in
Further, in this embodiment, even in the case of the communication system 102 (see
Further, in this embodiment, when receiving the reception data RX (from SYNC to CRC16H), since the communication part 11 performs control using the synchronization part IC that monitors the reception data RX, except when outputting the transmission data TX, transition control of the internal state may be performed based on the reception data RX.
Various technical features disclosed in this specification are not limited to the above-described embodiments but may be modified in various forms without departing from the spirit of the technical creation. That is, the above-described embodiments should be considered to be exemplary in all respects and not limitative. It should be understood that the technical scope of the present disclosure is not limited to the above-described embodiments, and encompasses all changes that fall within the meaning and range equivalent to the claims.
As described above, the semiconductor device (1) according to one aspect of the present disclosure comprises:
Further, the semiconductor device (1) according to one aspect of the present disclosure comprises:
Further, in the second configuration, the synchronization part (11C) may be configured to switch whether or not to perform synchronization control depending on whether or not the semiconductor device (1) is connected to a transmitting/receiving device (5) capable of communicating by a differential voltage method (third configuration,
Further, in the third configuration, the transmitting/receiving device may be a CAN transceiver (5) (fourth configuration).
Further, in the second configuration, the synchronization part (IC) may be configured to monitor the reception data as a result that the transmission data (TX) is input to the reception data (RX) (fifth configuration,
Further, the communication system (101) according to one aspect of the present disclosure comprises:
Further, in the sixth configuration, the transmitting/receiving device may be a CAN transceiver (5) (seventh configuration).
Further, the communication system (101) according to one aspect of the present disclosure comprises:
The present disclosure can be used, for example, in an in-vehicle communication system.
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the disclosures. Indeed, the embodiments described herein may be embodied in a variety of other forms. Furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the disclosures. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the disclosures.
Number | Date | Country | Kind |
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2022-183122 | Nov 2022 | JP | national |