JP2006140710A - Device and system for communication, and arbitrating method for communication - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate malfunction due to output of a device or system for communication even when the device or system is connected to a single signal line and to easily perform arbitration in case of a collision. <P>SOLUTION: When a one-wire communication device 12 serves as a transmission side and outputs a high level to an output portion Out, an NPN transistor 14 conducts between its collector and emitter. When another one-wire communication device 13 uses a communication line 11 having a low level, the low level is inputted to an input portion In, so transmission stops. The low level is inputted to a receiving means 26 only when a transmitting means 28 outputs the high level, so judgment for arbitration can easily be made. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a communication apparatus and communication system that perform transmission and reception through a single communication line and have an arbitration function, and a communication arbitration method.

  Conventionally, a one-wire communication circuit as shown in FIG. 8 has been used. The single communication line 1 can perform half-duplex digital signal communication between the communication means 2 and 3. However, it is assumed that there are other connections between the communication means 2 and 3 such as a ground or a power source. Each communication means 2, 3 is provided with a control unit including, for example, microcomputers 4, 5, and the communication line 1 becomes an interrupt input to the microcomputers 4, 5, and the counterpart communication means 2, 3 transmits a signal Only receive processing by interrupt processing. When a signal is transmitted to the communication means 2 and 3 on the other side, a digital signal is derived via an output port or the like. Although a buffer and the like are provided in the signal input / output path, they are omitted for the sake of simplicity.

  The communication line 1 connects the outputs of both the communication means 2 and 3 so as to have a wired OR relationship in which the low level is the active side. For this purpose, the communication lines 1 connect the inputs In of both communication means 2 and 3. Diodes 6 and 7 are connected between the output Out of each communication means 2 and 3 and the communication line 1, respectively. The directions of the anodes and cathodes of the diodes 6 and 7 are set to the forward direction when the output Out of the communication means 2 and 3 becomes active. That is, when the high level side of the power supply is a positive voltage, the diodes 6 and 7 connect the anode to the communication line 1 and connect the cathode to the output of the communication means 2 and 3.

  In each of the communication means 2 and 3, pull-up resistors 8 and 9 are connected between the input In and the high level side of the power source. As a result, when the outputs of both the communication means 2 and 3 are inactive, almost no current flows through the pull-up resistors 8 and 9, and the level of the communication line 1 becomes high. If the output Out of one or both of the communication means 2 and 3 becomes low level, a current flows to the pull-up resistors 8 and 9 via the diodes 6 and 7, and the communication line 1 becomes low level due to the voltage drop. Become. For simplification of explanation, the forward voltage of the diodes 6 and 7 is set to 0V, the power supply high level is set to 5V, the power supply low level is set to 0V, and the input impedance on the input In side of the communication means 2 and 3 is infinite. Assuming that the resistance value of the pull-up resistors 8 and 9 is 1 kΩ, a current of 5 mA flows through each of the pull-up resistors 8 and 9, and a total current of 10 mA flows to the output Out of the communication means 2 on the output side.

  Digital signal communication between the communication means 2 and 3 is possible in both directions, but at the same time, it becomes a half-duplex method which is possible only in one direction. That is, on the other hand, for example, the communication means 2 is a transmission side, and the other communication means 3 is a reception side. In the communication means 3 on the reception side, the output Out is set to the high level on the inactive side, and a digital signal transmitted via the communication line 1 from the output Out of the communication means 2 on the transmission side is received at the input In. When the output Out of the communication means 2 becomes the low level on the active side, the output Out of the communication means 2 passes through both the pull-up resistors 8 and 9 from the high level side of the power supply and further passes through the diode 6 on the communication means 2 side. Current flows, and the signal level of the communication line 1 connected to the input In of the communication means 3 becomes a low level. When the output Out of the communication means 2 becomes high level on the inactive side, almost no current flows through the diode 6, the signal level of the communication line 1 becomes high level, and the input In of the communication means 3 has high level. Given.

  FIG. 9 shows another example of the one-wire communication circuit (see, for example, Patent Document 1). 9, parts corresponding to those in FIG. 8 are denoted by the same reference numerals, and redundant description is omitted. In this example, only one pull-up resistor 8 is connected between the communication line 1 and the high level side of the power supply. The pull-up resistor 8 can be provided on either side of the communication means 2 and 3. Under the same conditions as in FIG. 8, the current that flows when the output Out of the communication means 2 and 3 on the transmission side is at a low level is 5 mA. 9, the basic operation of half-duplex digital signal communication via the communication line 1 is performed in the same manner as in FIG.

When performing half-duplex digital communication via the communication line 1, there is a multi-master protocol that can be used as a master for transmission by any communication means 2 and 3 as long as the communication line 1 is available. It has been adopted. A plurality of communication means 2 and 3 as nodes connected to a bus such as the communication line 1 are CSMA / CD (Carrier Sense Multiple Access with Collision).
Detection) method, the first node that accesses the bus acquires the transmission right. However, when transmissions from a plurality of nodes compete, it is necessary to arbitrate the transmission right.

FIG. 10 shows a schematic configuration of a data frame used for digital communication having an arbitration function. At the top is 1 bit of SOF (Start Of Frame), followed by an arbitration field based on identification information (ID). Furthermore, the control field (Control
Field), data field (Data), CRC field, ACK field and end of frame (EOF). In data frame transmission, arbitration of transmission rights is performed in the arbitration field, and data is transmitted in the data field.

  FIG. 11 is called CAN (Controller Area Network), and shows a concept of performing arbitration on a transmission right by transmission of an arbitration field in a data frame of a communication method using two communication lines. 8 and 9, two communication means 2 and 3 are connected to the communication line 1, but assuming that another communication means is connected, three nodes are connected to the bus. Assume that the nodes A to C start transmission at the same time from time t0 and contention occurs. In CAN, the potential difference between two communication lines is logically treated as having a preferential dominant level (D) and a receptive recessive level (R) as a bus level. Here, it is assumed that the high level is a recessive level and the low level is a dominant level. Different identification information (ID) is given to each node. From time t0, each node transmits 1-bit L level SOF, and then transmits identification information (ID). The identification information has a plurality of bits, and each bit is L level or H level, and the L level has priority over the H level. That is, even if a certain node outputs an H level, if there is another node that outputs an L level, the bus is at an L level.

  In FIG. 11, from time t0 to time t1, nodes A to C transmit identification information in which HL changes in the same manner. Therefore, the superiority or inferiority of the three nodes A to C is unknown. Even if node A outputs H level at time t1, the other nodes B and C output L level, so the bus becomes L level and node A loses and is switched from transmission to reception. Further, at time t2, since node C outputs H level and node B outputs L level, node C loses and is switched from transmission to reception. With these three parties, Node B will win and obtain the right to transmit to the end. A broken line shows a signal waveform when node A and node C continue transmission. When transmission from a plurality of nodes competes, priority is given to a node to which identification information is given so that a bit to be transmitted first is at L level (see, for example, Patent Documents 2 and 3).

  FIG. 12 shows a transmission procedure performed in each node in order to perform arbitration as shown in FIG. In CAN, an SOF is provided at the head of a data frame transmitted by each node, as shown in FIG. 10, and an arbitration field including an ID is provided next. In step s1 after the start of transmission, the bit of the signal to be transmitted next is prepared, and in step s2, the bit of the signal is transmitted. In step s3, it is determined whether or not the bit of the signal to be transmitted is an L output. When it is determined that the output is not the L output, that is, the H output, in step s4, the input of the received signal is checked. In step s5, it is determined whether the input check results in L input. When it is determined that the input is not the L input, that is, the H input, the process returns to step s1. When it is determined in step s3 that the output is L, the process returns to step s1. This is because at the time of L output, it is always determined that the input is L, and the presence of a node having priority over that node cannot be detected. Therefore, in step s4, an input check is performed only at H output. When it is determined in step s5 that there is an L input, it is detected that there is another L output node in spite of the H output. Therefore, if reception is performed in step s6 and the reception is completed, control is performed. End the procedure. If further transmission is necessary, a control procedure from the start of transmission is executed.

  FIG. 13 shows an overview of transmission processing and interruption processing for reception in the communication means 2 and 3 in FIG. FIG. 13A shows transmission processing, and signal preparation such as reading transmission data and the like is performed in step a1. In step a2, one bit to be transmitted next is extracted from the transmission data. If it is high level, Hi output is derived in step a3, and if it is low level, Lo output is derived in step a4. Next, in step a5, the next signal is prepared, and the process returns to step a2. Thereafter, step a2 to step a5 are repeated until the next signal disappears. In actual transmission processing, for example, data of a certain number of bits is set in the shift register in the signal preparation in step a1, and in steps a2 to a5, the data set in the shift register is shifted bit by bit. Just output. It is described that the signal level is judged at step a2 and either step a3 or step a4 is selected according to the signal level. When Lo output is performed at step a4, the communication means 2, 3 This is to clearly indicate that an interrupt to the microcomputers 4 and 5 occurs as indicated by the broken line.

  FIG. 13B shows interrupt processing for signal reception via the communication line 1. As shown in FIG. 8, since the communication line 1 is connected to the interrupt input Int of the microcomputers 4 and 5, when the communication line 1 becomes low level, the microcomputers 4 and 5 are interrupted and the interrupts are prohibited. Unless otherwise, interrupt the current process and interrupt the current process. In step b1, it is determined whether or not the communication means 2 and 3 themselves are performing Lo output in step a4 of FIG. If it is determined that it is not Lo output, a reception process for receiving a digital signal sent from the communication means 2 and 3 on the other side via the communication line 1 is performed in step b2. If it is determined in step b1 that the output is Lo output, the reception process is not performed. When the reception process of step b2 ends or when the reception process is not performed, the process returns to the process interrupted by the interrupt.

  FIG. 14 shows an outline of another example as a transmission process in each of the communication means 2 and 3 of FIGS. After signal preparation in step c1, for example, setting of data in the shift register, interrupt is prohibited in step c2. If the interrupt is prohibited, the interrupt process is not performed even if the interrupt input Int becomes low level. Step c3 to step c6 perform substantially the same operation as each step from step a2 to step a5 in FIG. That is, a signal for 1 bit is transmitted while shifting the shift register by 1 bit. However, since interrupt is prohibited in step c2, no interrupt is generated even if Lo output is performed in step c5. Therefore, in the reception process, it is not necessary to determine whether or not the terminal itself is Lo output as in step b1 in FIG.

Japanese Patent No. 2845000 Japanese Patent Laid-Open No. 8-18577 JP-A-9-135255

  Although the conventional one-wire communication circuit as shown in FIGS. 8 and 9 can perform transmission and reception by one communication line 1, the signal output for transmission is only the communication means on the transmission partner side. However, since it is also input to the communication means on the transmission side itself, a device for receiving only the signal from the other side is required. If the output of the communication means on the transmission side is confused with the signal from the other side, a malfunction may occur. As shown in FIG. 12, it takes time to determine whether or not it is the Lo output of itself during the interrupt process when receiving a signal from the other party. Further, if Lo output is performed in transmission, interrupt processing is activated, and it takes extra time to return from interrupt processing without performing reception processing. If interruption is prohibited immediately after the start of transmission, a signal from the other party cannot be received until the transmission of all signals is completed.

  As shown in FIG. 8, when the pull-up resistors 8 and 9 are provided in the communication means 2 and 3 on both sides of the communication line 1, respectively, for example, when only the communication means 2 performs Lo output, both pull-up resistors 8 and 9 are provided. , 9 flows, and the power consumption increases. If one pull-up resistor 8 is provided as shown in FIG. 9, the current flowing at the time of Lo output is half that of FIG. 8, and the power consumption is reduced. However, if only one pull-up resistor 8 is used, a current flows only between the pull-up resistor 8 and the output part of the communication means 2 and 3 that performs Lo output. As a result, the noise resistance is reduced. Further, if no current flows, the electrically insulating oxide film or the like cannot be removed at the contact portion, which may cause a contact failure.

  For example, if one communication means 2 becomes the transmission side and the other communication means 3 becomes the reception side, the communication means 2 side and the communication means 2 side will be relatively less than the connection portion between the communication line 1 and the pull-up resistor 8. Although a large current flows, almost no current flows from the connecting portion to the communication means 3 side. The part where the communication line 1 is connected to the output part or the input part of the communication means 2 and 3 is generally configured to be detachable by a terminal, a connector or the like. In the detachable part, electrical connection is made by contact between the conductors. If almost no current flows through the contact portion between the conductors, resistance increases due to oxidation of the contact portion, and contact failure tends to occur.

  Further, when arbitrating for collision avoidance between a plurality of nodes as shown in FIG. 11, as shown in step s3 of FIG. 12, the node determines whether or not the signal is L output immediately after sending out the signal. It is necessary to branch. Since the control procedure of FIG. 12 includes such a conditional branch, the operation is complicated. Since it is difficult to predict the result of conditional branching, it is difficult to increase the speed by pipeline processing in which program code is read, interpreted, and executed in parallel. This is because even if the program code is read in advance, if the result of the conditional branch differs from the prediction, it is necessary to read the program code from the branch destination again.

  An object of the present invention is to provide a communication device and a communication system, and a communication arbitration method capable of performing arbitration at the time of competition without causing malfunction due to its own output even when connected to a single signal line. It is to be.

In the present invention, when a plurality of communication lines can be connected to a single communication line whose logical level is predetermined in a free state and the communication line is free, the logical level changes between one side and the other side. In a communication device that can transmit information by signal,
Receiving means for receiving a signal from the communication line;
A transmission means for transmitting a signal to the communication line;
Provided between the receiving means and the transmitting means and the communication line, when the logic level of the signal transmitted from the transmitting means is on the one side, the signal from the communication line is input to the receiving means, and when the logic level is on the other side Switching means for switching so that one side of the logic level is input to the receiving means;
When the signal is not transmitted to the communication line, one side of the logical level is output from the transmitting unit, and when the other side of the logical level is input to the receiving unit when transmitting the signal, the transmission of the signal is stopped. And a control means for controlling the communication device.

  According to the present invention, a plurality of communication devices can be connected to a single communication line on one side whose logic level is predetermined in a free state. In the communication apparatus, if the communication line is free, in order to be able to transmit information with a signal that changes between one side and the other side of the logic level, a receiving unit, a transmitting unit, a switching unit, a control unit, Means. The switching means is provided between the receiving means for receiving the signal from the communication line and the transmitting means for transmitting the signal to the communication line, and when the logic level of the signal transmitted from the transmitting means is one side, When the logic level is on the other side, the signal is switched so that one side of the logic level is input to the receiving means. That is, if the other side of the logic level is output from the transmission unit, one side of the logic level is input to the reception unit regardless of the logic level of the signal line. If one side of the logic level is output from the transmission means, the logic level of the signal line is input to the reception means as it is. The control means outputs one side of the logic level from the transmission means when no signal is transmitted to the communication line, and transmits the signal when the other side of the logic level is input to the reception means when transmitting the signal. Since it is controlled to stop, it is not necessary to judge the logic level of the output from the transmission means, the control procedure can be shortened and simplified, and even if it is connected to a single signal line, its own There is no malfunction due to output, and arbitration at the time of competition can be easily performed.

  In the present invention, the control means causes the transmission means to transmit identification information set in advance by reflecting priority at the start of transmission, and during the transmission of the identification information, the reception means has the logic level. When the other side is input, the transmission is controlled to stop.

  According to the present invention, at the time when transmission of a signal via a single communication line is started, the control unit causes the transmission unit to transmit identification information set in advance by reflecting the priority. If the identification information is set so that the other side of the logic level is output to the communication means with high priority at an early stage, the other side of the logic level is input to the receiving means while the control means is transmitting the identification information. Then, control is performed so as to stop transmission, so that arbitration according to priority can be easily performed even if transmission conflicts.

In the present invention, the switching means includes
A diode connected between the communication line and the transmission means, and connected in a forward direction when the communication line is on one side of the logic level and the transmission means is on the other side of the logic level;
A switching unit and a control unit, wherein the switching unit is connected between the communication line and the receiving unit, the control unit is connected to the transmitting unit, and the logic level input to the control unit is one side or the other A switching element in which the switching unit is turned on or off depending on the side,
It is characterized by including.

  According to the invention, the switching means includes a diode and a switching element. The diode is connected between the communication line and the transmission means, and is connected in the forward direction when the communication line is on one side of the logic level and the transmission means is on the other side of the logic level. When the transmission means outputs the other side of the logic level when the logic level is one side, the forward direction is established, and the logic level of the communication line can be shifted to the other side by the output of the transmission means. When the communication line is not idle and the logic level is on the other side, even if the transmission means outputs one side of the logic level, the diode is reversed, and the output of the transmission means does not affect the communication line. do not do. The switching element has a switching unit and a control unit, the switching unit is connected between the communication line and the receiving unit, the control unit is connected to the transmitting unit, and the logic level input to the control unit is on one side The switching unit is turned on or off depending on the other side. If the output of the transmission means is one side of the logic level, the switching unit is turned on and the logic level of the communication line is input to the reception means. If the output of the transmitting means is the other side of the logic level, the switching unit is cut off, and the input of the receiving means is not the logic level of the communication line but the one side of the logic level. Accordingly, the other side of the logic level is input to the receiving means only when one side of the logic level is output from the transmitting means and the logic level of the communication line is on the other side.

In the present invention, the switching element is a bipolar transistor,
The bipolar transistor is characterized in that a collector is connected to the receiving means, a base is connected to the transmitting means, and an emitter is connected to the communication line.

  According to the present invention, the bipolar transistor is a switching element, the collector is connected to the receiving means, the base is connected to the transmitting means, and the emitter is connected to the communication line. When the transmitting means outputs one side of the logic level, a forward bias is applied to the base, and the collector and the emitter are electrically connected, and the communication line can be connected to the receiving means. When the transmitting means outputs the other side of the logic level, the forward bias is not applied to the base, and the receiving means is disconnected from the communication line.

In the present invention, a pull-up resistor is connected between the receiving means to which the switching unit of the switching element is connected and the high level side of the power source,
A pull-down resistor is connected between the communication line and the low level side of the power supply.

  According to the present invention, since the pull-up resistor is connected between the receiving means to which the switching unit of the switching element is connected and the high level side of the power supply, the transmitting means outputs the other side of the logic level and performs switching. When the element is cut off, the high level side of the power supply is input to the receiving means. If the communication line is free and is on one side of the logic level, the logic level of the communication line transitions to the output on the other side of the logic level from the transmitting means via a diode in the forward direction. If one side of the logic level is output from all the transmission means connected to the communication line, all the switching elements are turned on, and the communication line is on one side of the logic level. If there are transmission means connected to the communication line that output one side of the logic level and output that outputs the other side, the logic level of the communication line becomes the other side as a logical sum of the diodes. When the other side of the logic level is output from all the transmission means connected to the communication line, all the switching elements are cut off, and the communication line is connected only to the low level side of the power supply via the pull-down resistor. Serial data can be transmitted via a communication line with the high level side of the power supply as one side of the logic level and the low level side of the power supply as the other side of the logic level.

Furthermore, the present invention provides at least one communication means of a plurality of communication means to which the communication device according to any one of the foregoing is connected via the communication line,
The control means of the communication means transmits the identification information reflecting the priority at the start of transmission, and receives the other side of the logical level from the communication line while transmitting one side of the logical level of the identification information. For example, the communication system with an arbitration function is characterized in that transmission is stopped and arbitration is performed when contention occurs.

  According to the present invention, in a communication system with an arbitration function, a communication device that does not malfunction due to its own output and can easily perform arbitration at the time of competition as at least one communication means on a single communication line. Can be used. Even if a plurality of communication means are connected to the communication line, the control means of the communication means using the communication device transmits the identification information reflecting the priority at the start of transmission, and one of the logical levels of the identification information If the other side of the logic level is received from the communication line during transmission, the transmission is stopped and arbitration is performed when contention occurs. If communication information with high priority is given identification information so that the other side of the logical level is transmitted early, even if there is a conflict with other communication means with low priority, other communication means Arbitration can be performed so that the communication line can be used with priority.

Furthermore, the present invention connects a plurality of communication means to a single communication line whose logical level is predetermined on one side in a free state, and if any communication means has a free communication line, In the communication arbitration method that performs arbitration when transmission competes in communication that enables transmission of information with a signal that changes between the other side,
At least one communication means,
Receiving means for receiving a signal from the communication line;
A transmission means for transmitting a signal to the communication line;
Provided between the receiving means and the transmitting means and the communication line, when the logic level of the signal transmitted from the transmitting means is on the one side, the signal from the communication line is input to the receiving means, and when the logic level is on the other side Switching means for switching so that one side of the logic level is input to the receiving means;
When the signal is not transmitted to the communication line, one side of the logical level is output from the transmitting unit, and when the other side of the logical level is input to the receiving unit when transmitting the signal, the transmission of the signal is stopped. This is a communication arbitration method.

  According to the present invention, in communication performed by connecting a plurality of communication means to a single communication line whose logical level is predetermined in a free state, if any communication means is free, the logic Although it is possible to transmit information with a signal that changes between one side and the other side of the level, a plurality of communication means determine that the communication line is idle, and contention for transmission that simultaneously starts transmission occurs. Mediation is required. At least one of the plurality of communication means connected to the communication line is provided with a switching means together with a reception means and a transmission means for receiving and transmitting signals with respect to the communication line. The switching means is provided between the receiving means and the transmitting means and the communication line. When the logic level of the signal transmitted from the transmitting means is on one side, the signal from the communication line is input to the receiving means, and the logic level is on the other side. In this case, the receiving means is switched so that one side of the logic level is input. When the logic level of the signal output from the transmitting means to the communication line is on one side, the switching means switches so that the signal from the communication line is input to the receiving means, so the logic level of the signal line is on the other side. Then, it can be seen that the other side of the logic level is input to the receiving unit, and the other communication unit outputs the other side of the logic level via the communication line. When the other side of the logic level is input to the receiving means and it is known that the other communication means is using the communication line, the transmission is stopped, so that arbitration can be performed so as to avoid contention.

  According to the present invention, the other side of the logic level is input to the receiving means only when the transmitting means transmits one side of the logic level and the communication line is on the other side of the logic level. Since control is performed so that signal transmission is stopped when the logical level input to the receiving means is on the other side, it is not necessary to determine the logical level of the output from the transmitting means, and the control procedure is shortened and simplified. In addition, even if connected to a single signal line, there is no malfunction due to its own output, and arbitration at the time of contention can be easily performed.

  According to the present invention, even if contention occurs at the start of transmission of a signal via a single communication line, identification information set in advance by reflecting priority is transmitted from the transmission unit, and the response is made according to the priority. Arbitration can be performed easily.

  According to the present invention, the switching means includes a diode and a switching element. When the communication line is on one side of the logic level and the transmitting means is on the other side of the logic level, the communication means is connected via the forward direction and the diode. If the logic level is one side, it is possible to make a transition to the other side, cut off the switching element, and input one side of the logic level to the receiving means. When the communication line is not idle and the logic level is on the other side, even if the transmission means outputs one side of the logic level, the diode is reversed, and the output of the transmission means does not affect the communication line. do not do. If the output of the transmission means is one side of the logic level, the switching unit is turned on and the logic level of the communication line is input to the reception means. The other side of the logical level is input to the receiving means only when the one side of the logical level is output from the transmitting means and the logical level of the communication line is on the other side. It can be easily confirmed that the other side of the logic level is output to the communication line. Since the switching unit of the switching element is cut off when the output of the transmission unit is on the other side of the logic level, even if one side of the logic level is input to the reception unit, the current flowing between the transmission unit and the reception unit is Less power consumption can be reduced.

  According to the present invention, the collector of the bipolar transistor is connected to the receiving means, the base is connected to the transmitting means, the emitter is connected to the communication line, and the receiving means and the communication line are connected according to the logic level output from the transmitting means. Can be switched between.

  Further, according to the present invention, serial data can be transmitted via a communication line, with the high level side of the power source set as one side of the logic level and the low level side of the power source set as the other side of the logic level.

  Furthermore, according to the present invention, a communication device that is free from malfunction due to its own output and that can easily perform arbitration during competition is used as at least one of a plurality of communication means, and a single communication line is used. It can connect so that communication is possible. The control means of the communication means using the communication device can easily perform arbitration by transmitting the identification information reflecting the priority at the start of transmission.

  Furthermore, according to the present invention, in communication performed by connecting a plurality of communication means to a single communication line having a predetermined logical level in one idle state, transmission is performed if any communication means is free. Signals can be transmitted using the multi-master protocol that is possible. Arbitration at the time of transmission competition can be easily performed by stopping transmission if the logic level of the signal line input to the receiving means is on the other side.

  FIG. 1 shows a schematic electrical configuration of a one-wire communication system 10 according to an embodiment of the present invention. In the one-wire communication system 10, apparently, half-duplex digital signal communication is performed between the plurality of one-wire communication devices 12 and 13 via the single communication line 11. Each one-wire communication device 12 and 13 includes an input unit In and an output unit Out. Input portions In of the one-wire communication devices 12 and 13 are connected to collectors of bipolar NPN transistors 14 and 15, respectively. A communication line 11 is connected between the emitters of the NPN transistors 14 and 15. Diodes 16 and 17 are connected between the emitters of the NPN transistors 14 and 15 and the output part Out of the one-wire communication devices 12 and 13, respectively. The diodes 16 and 17 are connected such that the anode is on the communication line 11 side and the cathode is on the output unit Out side of the communication means 12 and 13. The collectors of the NPN transistors 14 and 15 are also connected to the positive voltage side of the power supply via the pull-up resistors 18 and 19. The bases of the NPN transistors 14 and 15 are connected to the output units Out of the one-wire communication devices 12 and 13 via current limiting base resistors 20 and 21, respectively.

  In each one-wire communication device 12, 13, NPN transistors 14, 15, diodes 16, 17, pull-up resistors 18, 19, and base resistors 20, 21 form switching means 22, 23, respectively. The one-wire communication devices 12 and 13 are respectively provided with microcomputers 24 and 25 serving as control means. Receiving means 26 and 27 and transmitting means 28 and 29 are provided in the input part In and the output part Out of each one-wire communication device 12 and 13, respectively.

  That is, the switching means 22 and 23 include diodes 16 and 17 and NPN transistors 14 and 15 as switching elements. The diodes 16 and 17 are connected between the communication line 11 and the transmission means 28 and 29. The communication line 11 is at the high level, that is, one side of the logic level, and the transmission means 28 and 29 are at the low level, that is, the other at the logic level. If the transmission means 28 and 29 output the other side of the logical level when the communication line 11 is idle and the logical level is one side, the forward direction is established. The logic level of the line 11 can be shifted to the other side by the outputs of the transmitting means 28 and 29. When the communication line 11 is not in an idle state and the logic level is on the other side, even if the transmission means 28 and 29 output one side of the logic level, the diodes 16 and 17 are in the opposite direction, and the transmission means 28 , 29 does not affect the communication line 11. The NPN transistors 14 and 15 which are switching elements have a switching unit formed by a collector and an emitter and a control unit formed by a base, and the switching unit is provided between the communication line 11 and the receiving means 26 and 27. Connected, the control unit is connected to the transmission means 28, 29, and the switching unit is turned on or off depending on whether the logic level input to the control unit is one side or the other side. If the output of the transmission means 28, 29 is one side of the logic level, the switching unit is turned on, and the logic level of the communication line 11 is input to the reception means 26, 27. If the outputs of the transmitting means 28 and 29 are on the other side of the logic level, the switching unit is cut off, and the inputs of the receiving means 26 and 27 are on the one side of the logic level instead of the logic level of the communication line 11. Therefore, the other side of the logic level is input to the receiving means 26 and 27 when one side of the logic level is output from the transmitting means 28 and 29 and the logic level of the communication line 11 is the other side. Limited.

  Although not shown, the one-wire communication devices 12 and 13 share a common ground. Each of the one-wire communication devices 12 and 13 is connected individually or commonly to a power source that generates a predetermined high-level positive voltage with reference to the ground potential. The pull-up resistors 18 and 19 connect the input part In to the positive voltage side of such a power supply. Therefore, in actual digital signal transfer, at least the ground functions as a signal return path.

  In the one-wire communication system 10 of FIG. 1, when the output units Out of the one-wire communication devices 12 and 13 on both sides of the communication line 11 output both high levels that are one logical state, the logical state of the communication line 11 is also high. Become a level. When the output unit Out is at a high level, the base, which is the control unit of the NPN transistors 14 and 15, is biased in the forward direction, and the switching unit between the collector and the emitter is in a conductive state and is in a low impedance state. However, since the communication line 11 is also at a high level, the current flowing through the collectors and emitters of the pull-up resistors 18 and 19 and the NPN transistors 14 and 15 to the communication line 11 is small, and the voltage at the pull-up resistors 18 and 19 is low. The drop is also reduced, and a high level is input to the input unit In of the one-wire communication devices 12 and 13.

  When one communication means, for example, the one-wire communication device 12 becomes a transmission side and the low level which is the other logic state is output to the output unit Out, the base of the NPN transistor 14 is connected to the high-level communication line 11. It is biased with a voltage in the reverse direction with respect to the emitter, and the collector-emitter is cut off and becomes high impedance. The diode 16 is biased in the forward direction and becomes conductive, and a current flows from the communication line 11 to the output unit Out of the one-wire communication device 12 to change the logic state of the communication line 11 to a low level. The current flowing through the communication line 11 is supplied from the positive voltage side of the power supply via the collector-emitter of the NPN transistor 15 on the other one-sided communication device 13 side and the pull-up resistor 19. Due to the voltage drop due to this current, the logic state of the input unit In of the one-year communication device 13 becomes a low level. If the logic state of the output unit Out of the one-wire communication device 13 is high, the NPN transistor 15 continues to be in a conductive state, and the diode 17 between the communication line 11 and the output unit Out is biased in the reverse direction so as to be in a cut-off state. to continue. If a high-level logic state is output from the output unit Out of the one-wire communication device 12, even if the collector-emitter state of the NPN transistor 15 continues to be conductive, the logic state of the communication line 11 becomes high level. The current flowing between the collector and the emitter of the pull-up resistor 19 and the NPN transistor 15 decreases, and the logic state of the input unit In of the one-wire communication device 13 becomes a high level.

  In this way, if the one-wire communication device 13 outputs a high level from the output unit Out, the input unit In receives a digital signal transmitted from the one-wire communication device 12 connected via the communication line 11. be able to. Similarly, the one-wire communication device 12 can also receive a digital signal transmitted from the one-wire communication device 13 at the input unit In by outputting a high level from the output unit Out.

  When one output unit Out of the one-wire communication devices 12 and 13 is at a low level and the other output unit is at a high level, a high-level side pull-up resistor, an NPN transistor, a communication line, and a low-level side diode Although a current flows in a path from the low level side output unit Out to the low level side output unit Out, the current through the pull-up resistor does not flow because the low level side NPN transistor is cut off. Therefore, no current flows through both pull-up resistors as described in FIG. 8, and power consumption can be reduced. Since the current flowing through the communication line 11 flows in the same way as in FIG. 8, the same communication quality can be maintained in terms of noise resistance.

  FIG. 2 shows a transmission procedure in the case where the one-wire communication devices 12 and 13 of the present embodiment are each node in order to perform arbitration as shown in FIG. In step t1 after the start of transmission, the bit of the signal to be transmitted next is prepared, and in step t2, the bit of the signal is transmitted. At step t3, input check of received signals is performed. In step t4, it is determined whether or not the input is L as a result of the input check. When it is determined that the input is not the L input, that is, the H input, the process returns to step t1. In the one-wire communication apparatuses 12 and 13 according to the present embodiment, the L input is always determined at L output, and the presence of a node having priority over that node is detected. If it is determined at step t4 that the input is L, the node itself has an H output, but another L output node exists. Therefore, if reception is performed at step t5 and reception ends. The control procedure is terminated once. If further transmission is necessary, a control procedure from the start of transmission is executed.

  When the control procedure shown in FIG. 2 is compared with the procedure shown in FIG. 12, in the control procedure of FIG. 2, as shown in step s3 of FIG. There is no need to branch by judging. Since the control procedure of FIG. 12 includes such a conditional branch, the operation is complicated. Since it is difficult to predict the result of conditional branching, it is difficult to increase the speed by pipeline processing in which program code is read, interpreted, and executed in parallel. This is because even if the program code is read in advance, if the result of the conditional branch differs from the prediction, it is necessary to read the program code from the branch destination again. Since the branch condition is simplified, it is possible to form a logic circuit capable of corresponding operation instead of program operation.

  FIG. 3 shows the reason for using the NPN transistor 14 in FIG. One of the conditions for the input unit In to be at the low level Lo is that the output unit OutA is at the high level Hi and the output unit OutB is at the low level Lo. However, this condition is not satisfied because OutA and OutB are connected as the output unit Out. Another condition is that the output unit OutA is at the high level Hi and the output unit OutC is at the low level Lo. At this time, the input unit In is at the low level Lo. The output unit OutC is actually the output unit Out of the communication unit 13 shown in FIG. Therefore, when the communication means 12 is on the receiving side, the output unit Out is set to high level, OutA = OutB = Hi, and the digital signal from the output unit Out of the communication means 13 on the transmitting side is transmitted to the communication line 11 and the NPN transistor. Can be received by the input unit In via a communication line passing between the emitter and the collector. When the output unit Out of the partner communication unit 13 is at a high level, the communication unit 12 becomes a transmission side via the communication line 11 to transmit a digital signal from the output unit Out, and the communication unit 13 of the reception side It can be received by the input unit In. When the output part Out of both the communication means 12 and 13 outputs a low level, what is called a collision arises. As a countermeasure when a collision occurs, the one already considered in the one-wire communication circuit of FIGS. 6 and 7 can be used.

  FIG. 4 shows a schematic electrical configuration of a one-wire communication system 30 according to another embodiment of the present invention. In the present embodiment, parts corresponding to those in the embodiment of FIG. In this embodiment, a pull-down resistor 31 having a relatively large resistance value is connected to the communication line 11 so that the communication line 11 is surely at a low level when the outputs of both the communication means 12 and 13 are at a low level. ing. The resistance value of the pull-down resistor 31 is such that when the output part Out of both the communication means 12 and 13 is at a high level, both NPN transistors 14 and 15 are in a conductive state, and current flows through the pull-up resistors 18 and 19. However, it is limited by the pull-down resistor 31 so that the voltage drop at the pull-up resistors 18 and 19 is small, and the input portion In remains in the high level range.

  FIG. 5 shows the internal configuration of the one-wire communication devices 12 and 13 used in the one-wire communication system 10 and 30 of the embodiment of FIG. 1 or FIG. 4 and the operation as still another embodiment. As shown in FIG. 5A, the one-wire communication devices 12 and 13 include a microcomputer 40 for communication control. The microcomputer 40 has a start input Int for starting interrupt processing. The input unit In of the one-wire communication devices 12 and 13 is connected to the interrupt process activation input Int of the microcomputer 40. A buffer or the like can be interposed in the middle of this connection. The microcomputer 40 is also provided with an output port Out, and is connected to the output unit Out of the one-wire communication devices 12 and 13. A buffer or the like can be interposed in the middle of this connection. In the embodiment shown in FIGS. 1 and 4, a low level input to the input unit In of the one-wire communication devices 12 and 13 starts an interrupt process in the microcomputer 40. As described above, the one-wire communication devices 12 and 13 do not set the input unit In to the low level when the output unit Out of the one-wire communication devices 12 and 13 derives the output of the low level. Even then, interrupt processing can be activated to prevent malfunction. Therefore, the Lo output at step a4 does not necessarily generate an interrupt as shown in FIG. 13A, and the determination at step b1 of FIG. 13B is not necessary. If an interrupt is generated, only reception processing is performed. Should be done.

  FIG. 5B shows an embodiment in which further power-saving power saving is realized by controlling the output unit Out by the microcomputer 40 of FIG. When the one-wire communication devices 12 and 13 are on the receiving side and output a high level from the output unit Out, the signal on the communication line 11 is output from the counterpart one-wire communication devices 12 and 13 to a low level from time t10. Assume a changing case. If reception processing by the one-wire communication devices 12 and 13 on the receiving side is possible by time t11, the output unit Out is changed to a low level after time t11, and the pulling by the receiving side is performed during the period from time t11 to time t12. Power saving can be realized by preventing current from flowing through the up resistor. If the output unit Out on the reception side is kept at the high level after time t11, the NPN transistor on the reception side continues to be conductive, and the output unit Out on the transmission side is connected via the communication line from the pull-up resistor and the NPN transistor on the reception side. Current continues to flow. If the output unit Out on the reception side is changed to a low level at time t11, the NPN transistor on the reception side can be turned off to cut off this current. Until time t12, since the output unit Out is at a low level on the transmission side, the NPN transistor on the transmission side is in a cut-off state, and thus the power saving state can be continued from time t11 to time t20. Since the output unit Out on the transmission side becomes high level at time t12, if the output unit Out on the reception side also returns to high level, the current hardly flows until time t20 when the transmission side sets the output to low level next time. Can continue. The time after time t21 may be the same as after time t11.

  FIG. 6 shows a schematic control procedure by the microcomputers 24, 25; 40 when transmitting the data frame as shown in FIG. 10 in the one-wire communication system 10, 30 of FIG. In step u1, it is determined whether or not the communication line 11 is free. Whether or not the communication line 11 is free is determined by a high level state continuing for a predetermined time or more. If it is determined in step u1 that the communication line 11 is free, 1 bit of SOF is transmitted in step u2. In step u3, it is determined whether or not an arbitration field remains. If the arbitration field remains, the remaining head 1-bit signal is transmitted in step u4. In step u5, it is determined whether or not a low level is input to the input unit In. If the low level is not input, the process returns to step u3. If it is determined in step u5 that a low level has been input, the process proceeds to reception in step u6. When it is determined in step u3 that no arbitration field remains, in step u7, the remaining control fields and thereafter are transmitted.

  FIG. 7 shows a schematic electrical configuration of a one-wire communication system 50 as still another embodiment of the present invention. In the present embodiment, parts corresponding to those in the embodiment of FIG. 1 or FIG. One-wire communication devices 51 and 52 connected via a single communication line 11 include NPN transistors 14 and 15, diodes 16 and 17, operation switches 53 and 54, first display loads 55 and 56, Second display loads 57 and 58 and bias resistors 59 and 60 are included, respectively. The first display loads 55 and 56 and the second display loads 57 and 58 are realized by a bell or buzzer that displays sound, or a lamp or light emitting diode (LED) that displays light.

  First display loads 55 and 56 are respectively connected between the collectors of the NPN transistors 14 and 15 and the positive voltage side of the power supply, and bias resistors 59 and 60 are respectively connected between the base and the positive voltage side. . The emitters of the NPN transistors 14 and 15 are connected by the communication line 11, and the diodes 16 and 17, the second display loads 57 and 58, and the operation switches 53 and 54 are connected between the emitter and the ground, respectively. The series circuits of the diodes 16 and 17 and the second display loads 57 and 58 are connected to one ends of the operation switches 53 and 54, respectively, and this connection is also connected to the bases of the NPN transistors 14 and 15. The other ends of the operation switches 53 and 54 are grounded.

  When both the operation switches 53 and 54 are turned off, a forward bias voltage is applied to the bases of the NPN transistors 14 and 15 from the positive voltage side of the power supply via the bias resistors 59 and 60, thereby turning on. . However, since the emitter side and the ground are cut off, no current flows through the first display loads 55 and 56 and the second display loads 57 and 58, and display is not performed. On the other hand, for example, when the operation switch 53 on the one-wire communication device 51 side is operated from OFF to ON, the base of the NPN transistor on the one-wire communication device 51 side is grounded and cut off. Since the NPN transistor 15 continues to be conductive on the one-wire communication device 52 side to which the two display loads 57 are connected via the communication line 11, the first display load 56 and the NPN transistor 15 are connected from the positive voltage side of the power supply. A current flows between the collector and the emitter, and the operation switch 53 reaches the ground. By this current, display is performed on the first display load 56 on the one-wire communication device 52 side and the second display load 57 on the one-wire communication device 51 side. The display on the second display load 57 can confirm that the display is performed on the first display load 56 of the counterpart one-wire communication device 52 via the communication line 11.

  When the other one-wire communication device 52 is operated from OFF to ON by operating the operation switch 54, the base of the NPN transistor 15 is grounded, the NPN transistor 15 is cut off, the first display load 56, the NPN transistor 15 The current path flowing between the collector-emitter, the communication line 11, the diode 16, the second display load 57, and the operation switch 53 is also cut off, and the display of the first display load 56 is stopped and the second display load is stopped. The display at 57 is also stopped, and it can be confirmed that the display at the one-wire communication device 52 on the other party is stopped.

  When both the operation switches 53 and 54 are ON, the first display loads 55 and 56 and the second display loads 57 and 58 are all stopped. In this state, when the operation switch 53 on the one-wire communication device 51 side is turned OFF, the base of the NPN transistor 14 is biased forward and becomes conductive, and the first display load 55 and the NPN transistor are connected from the positive voltage side of the power supply. Current flows to the ground via the collector-emitter 14, the communication line 11, the diode 17, the second display load 58, and the ON operation switch 54, and the first display load 55 and the second display load 58 Display is performed. Further, when the operation switch 54 is operated from ON to OFF, the display is stopped at all of the first display loads 55 and 56 and the second display loads 57 and 58.

  The one-wire communication system 50 according to the present embodiment can perform communication such as sending a signal in a ring type using a bell or a buzzer as the first display loads 55 and 56. If illumination is performed as the first display loads 55 and 56, the illumination can be turned on / off at a remote position. Even if the display state of the first display loads 55 and 56 cannot be confirmed directly only by the operation state of the operation switches 53 and 54, it can be confirmed by the second display loads 57 and 58.

  Even in the one-wire communication system 50 of the present embodiment, when the operation switches 53 and 54 are OFF, when the display is performed with the first display loads 55 and 56, arbitration can be performed by transferring the transmission right to the other party. it can.

  In the above description of the embodiments, the one-wire communication devices 12, 13; 51, 52 are provided on both sides of the single communication line 11, but three or more one-wire communication devices are provided on the single communication line 11. It can also be connected. Even when three or more one-wire communication devices are connected, it is possible to obtain the same effect of preventing malfunctions due to its own output and power saving by reducing the current flowing through itself. It is also possible to easily perform arbitration with the same logic judgment as communication using a simple communication standard.

  In addition, although an NPN type bipolar transistor is used as the switching element, other switching elements such as an n-channel MOSFET can be used. Further, although the positive voltage side is set to the high level, the polarity of the voltage can be changed as necessary so that the negative voltage side is set to the high level, for example. When the polarity is changed, the conduction type of the switching element may be changed to, for example, a PNP bipolar transistor or a p-channel MOSFET in accordance with the polarity.

1 is a block diagram showing a schematic electrical configuration of a one-wire communication system 10 according to an embodiment of the present invention. It is a flowchart which shows the control procedure which transmits by the one-wire communication apparatuses 12 and 13 of FIG. It is an electric circuit diagram which shows the reason for using the NPN transistor 14 with the one-wire communication apparatus 12 of FIG. It is a block diagram which shows schematic electrical structure of the one-wire communication system 30 which is the other form of implementation of this invention. It is a block diagram which shows the internal structure of the one wire communication apparatuses 12 and 13 shown in FIG. 1 and FIG. 4, and the wave form diagram which shows the operation | movement as another form of implementation of this invention. 11 is a flowchart showing a schematic control procedure for transmitting the data frame of FIG. 10 in the embodiment of FIGS. 1 and 4. It is an electric circuit diagram which shows the schematic electrical constitution of the one wire communication circuit 50 as further another form of implementation of this invention. It is a block diagram which shows the schematic electrical constitution of the conventional one-wire communication circuit. It is a block diagram showing a schematic electrical configuration of another conventional one-wire communication circuit. It is a figure which shows the structure of the data frame of CAN in digital communication. It is a time chart which shows the example of the mediation performed at the time of a competition in CAN. It is a flowchart which shows the rough control procedure which transmits data by CAN. 9 is a flowchart showing schematic procedures of transmission processing and interrupt processing in the one-wire communication circuit of FIG. 8. It is a flowchart which shows the schematic procedure of the other transmission process in the one wire communication circuit of FIG.

Explanation of symbols

10, 30, 50 One-wire communication system 11 Communication line 12, 13, 51, 52 One-wire communication device 14, 15 NPN transistor 16, 17 Diode 18, 19 Pull-up resistor 22, 23 Switching means 24, 25, 40 Microcomputer 26, 27 Receiving means 28, 29 Transmitting means 31 Pull-down resistor 53, 54 Operation switch 55, 56 First display load 57, 58 Second display load

Claims (7)

A plurality of communication lines can be connected to a single communication line on one side whose logic level is predetermined in a free state, and if the communication line is free, information is transmitted with a signal that changes between one side and the other side of the logic level. In a communication device that can transmit,
Receiving means for receiving a signal from the communication line;
A transmission means for transmitting a signal to the communication line;
Provided between the receiving means and the transmitting means and the communication line, when the logic level of the signal transmitted from the transmitting means is on the one side, the signal from the communication line is input to the receiving means, and when the logic level is on the other side Switching means for switching so that one side of the logic level is input to the receiving means;
When the signal is not transmitted to the communication line, one side of the logical level is output from the transmitting unit, and when the other side of the logical level is input to the receiving unit when transmitting the signal, the transmission of the signal is stopped. And a control means for controlling the communication device.   The control means causes the transmitting means to transmit identification information set in advance by reflecting priority at the start of transmission, and the other side of the logical level is input to the receiving means during transmission of the identification information. The communication apparatus according to claim 1, wherein control is performed to stop transmission. The switching means is
A diode connected between the communication line and the transmission means, and connected in a forward direction when the communication line is on one side of the logic level and the transmission means is on the other side of the logic level;
A switching unit and a control unit, wherein the switching unit is connected between the communication line and the receiving unit, the control unit is connected to the transmitting unit, and the logic level input to the control unit is one side or the other A switching element in which the switching unit is turned on or off depending on the side,
The communication device according to claim 1, further comprising: The switching element is a bipolar transistor;
4. The bipolar transistor according to claim 1, wherein a collector is connected to the receiving means, a base is connected to the transmitting means, and an emitter is connected to the communication line. Communication equipment. A pull-up resistor is connected between the receiving means to which the switching unit of the switching element is connected and the high level side of the power supply,
The communication apparatus according to claim 1, wherein a pull-down resistor is connected between the communication line and a low level side of the power source. The communication device according to any one of claims 1 to 5 serves as at least one communication unit among a plurality of communication units connected via the communication line,
The control means of the communication means transmits the identification information reflecting the priority at the start of transmission, and receives the other side of the logical level from the communication line while transmitting one side of the logical level of the identification information. A communication system with an arbitration function, wherein transmission is stopped and arbitration is performed when contention occurs. When a plurality of communication means are connected to a single communication line that is preliminarily set to one side in which the logic level is predetermined, and if any communication means has a free communication line, it is between one side and the other side of the logic level. In the communication arbitration method that performs arbitration when transmission competes in communication that enables transmission of information with a signal that changes in
At least one communication means,
Receiving means for receiving a signal from the communication line;
A transmission means for transmitting a signal to the communication line;
Provided between the receiving means and the transmitting means and the communication line, when the logic level of the signal transmitted from the transmitting means is on the one side, the signal from the communication line is input to the receiving means, and when the logic level is on the other side Switching means for switching so that one side of the logic level is input to the receiving means;
When the signal is not transmitted to the communication line, one side of the logical level is output from the transmitting unit, and when the other side of the logical level is input to the receiving unit when transmitting the signal, the transmission of the signal is stopped. A communication arbitration method characterized by the above.

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