JP2016010137A - Termination resistance value setting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a termination resistance value setting device which determines a resistance value of a termination resistor adapted to a real communication environment.SOLUTION: A termination resistance value setting section 1 includes: a resistance value change part 13 which increases and decreases a resistance value of a variable termination resistor 3 step by step each time a response signal receiving part 12 receives a response signal to a command transmitted from a command transmission part 11; and a storage part 20 for storing a maximum value and a minimum value of the resistance value within a range in which the response signal can be received, for each node 7. The resistance value is determined between an upper limit value that is a smallest value among the maximum values of the nodes 7 and a lower limit value that is a greatest value among the minimum values of the nodes 7.

Description

  The present invention relates to a termination resistance value setting device that can optimally determine the resistance value of a termination resistor connected to the end of a network to which a plurality of nodes are connected.

  A termination resistor is required at the end of the network where the number of connection nodes is 1: N (N is a natural number) in order to suppress the influence of reflected waves due to signal reflection. However, when the resistance value of the termination resistor is a fixed value determined by a standard or the like, the termination resistor may not be adapted to the actually established communication environment, and thus there is a problem that a communication error occurs.

  Thus, various attempts have been made to change the termination resistance in accordance with individual communication environments. For example, Patent Literature 1 discloses a bus line termination circuit that changes a termination resistance depending on the number of connected loads. The bus line termination circuit includes a detecting means for detecting the number of loads connected to the bus line, a plurality of resistors, and the detected connected load for obtaining an optimum combined resistance value for terminating the bus line. Resistance switching means for switching the connection state between the plurality of resistors and the bus line in accordance with the number of resistors.

JP 2000-151721 A (published on May 30, 2000)

  However, the prior art as described above changes the resistance value of the termination resistor only by the number of connected loads, and the communication environment such as the length of the wiring, the type of wiring, etc. is used to determine the resistance value. Not considered. For this reason, when the network is actually constructed, there is a problem in that the terminating resistor does not match the network and a communication error occurs. In view of the above problems, an object of the present invention is to provide a termination resistance value setting device that determines a resistance value of a termination resistance suitable for an actual communication environment.

  In order to solve the above problem, a terminal resistance value setting device according to an aspect of the present invention includes a variable resistor installed in a network to which a plurality of nodes are connected, and a resistance value that determines a resistance value of the variable resistor. A determination unit, a transmission unit that transmits a command to each of the nodes, a reception unit that receives a response signal from each of the nodes in response to the command transmitted by the transmission unit, and every time the reception unit receives the response signal A first control for continuously increasing the resistance value in a range in which the receiving unit can receive the response signal in a range in which the receiving unit can receive the response signal, and stepwise each time the receiving unit receives the response signal. In addition, the second control for causing the receiving unit to continue the variable resistor within the range in which the receiving unit can receive the response signal is performed so that one of them is first and for each of the nodes. Resistance A value change unit, and a storage unit that stores a maximum value and a minimum value of the resistance value when the response signal is receivable for each of the nodes, and the resistance value determination unit is stored in the storage unit. In addition, the smallest value among the maximum values for each of the nodes is set as an upper limit value, and the largest value among the minimum values for each of the nodes stored in the storage unit is set as a lower limit value. The resistance value is determined between the upper limit value and the lower limit value for the node where the minimum value that is less than or equal to the value and the maximum value that is greater than or equal to the lower limit value are obtained.

  According to the above configuration, the terminal resistance value setting device increases the resistance value of the variable resistor stepwise every time the receiving unit receives the response signal, and the variable resistance within the range in which the receiving unit can receive the response signal. And a second control for allowing the receiving unit to continue to reduce the resistance value of the variable resistor stepwise every time the receiving unit receives the response signal. Control is performed for each node so that either one comes first. In addition, by the operation of increasing or decreasing the resistance value of the variable resistor by the first control and the second control, the maximum value and the minimum value of the resistance value of the variable resistor at each node capable of receiving the response signal are obtained and stored in the storage unit. . Therefore, in a state where the communication network is actually constructed, a resistance value that does not match the communication environment is included in the variable range of the resistance value of the variable resistor, and communication is performed at each node where the communication range is overlapped. It is possible to grasp the maximum and minimum resistance values of the variable resistor that can be normally performed.

  Further, the termination resistance value setting device determines the resistance value of the variable resistor between the smallest value (upper limit value) of the maximum resistance value of the variable resistor and the largest value (lower limit value) of the minimum value. Therefore, the resistance value of the variable resistor can be determined within a range in which each node connected to the communication network can normally communicate. As a result, the resistance value of the variable resistor suitable for the actual communication environment can be determined. Thereby, it is possible to prevent a communication error caused by the fact that the resistance value of the termination resistor is not suitable for the communication network, as in the case where the resistance value of the conventionally determined termination resistor is adopted.

  In order to solve the above-described problem, a terminal resistance value setting device according to an aspect of the present invention determines a variable resistor installed at a terminal of a network to which a plurality of nodes are connected, and a resistance value of the variable resistor. A resistance value determination unit; a transmission unit that transmits a command to each of the nodes at a time; a reception unit that receives a response signal from each of the nodes in response to the command transmitted by the transmission unit; and a predetermined time from the transmission of the command The first control for causing the variable resistor to continue the operation of increasing the resistance value step by step every time the variable resistor is in a variable range of the resistance value of the variable resistor, and stepwise every time a certain time has elapsed from the transmission of the command. The second control for causing the variable resistor to continue the operation of decreasing the resistance value in the variable range of the resistance value of the variable resistor is performed so that one of them is first, and for each of the nodes in parallel. A resistance value changing unit, and a storage unit that stores the resistance value when the response signal is receivable for each of the nodes, and the resistance value determining unit is stored in the storage unit. The smallest value among the maximum resistance values for the node is set as the upper limit value, and the largest value among the minimum resistance values for the nodes stored in the storage unit is set as the lower limit value. The resistance value is determined between the upper limit value and the lower limit value for the node from which the minimum value equal to or lower than the upper limit value and the maximum value equal to or higher than the lower limit value are obtained. .

  According to the above configuration, the termination resistance value setting device can receive the response signal when the receiving unit performs an operation of increasing the resistance value of the variable resistor stepwise every time a certain time has elapsed since the transmission of the command from the transmitting unit. The receiving unit can receive the response signal in the first control for allowing the variable resistor to continue within a certain range and the operation of decreasing the resistance value of the variable resistor stepwise every time a certain time has elapsed since the transmission of the command from the transmitting unit. The second control in which the variable resistance is continued in the range is performed in parallel for all the nodes so that one of them comes first. Further, the resistance value of the variable resistor at each node capable of receiving the response signal is obtained and stored in the storage unit by the operation of increasing or decreasing the resistance value of the variable resistor by the first control and the second control. Therefore, in the state where the communication network is actually constructed, the resistance value of the variable resistor that can normally perform communication can be grasped at each node where the communicable ranges overlap.

  Further, the termination resistance value setting device determines the resistance value of the variable resistor between the smallest value (upper limit value) of the maximum resistance value of the variable resistor and the largest value (lower limit value) of the minimum value. Therefore, the resistance value of the variable resistor can be determined within a range in which each node connected to the communication network can normally communicate. As a result, the resistance value of the variable resistor suitable for the actual communication environment can be determined. Thereby, it is possible to prevent a communication error caused by the fact that the resistance value of the termination resistor is not suitable for the communication network, as in the case where the resistance value of the conventionally determined termination resistor is adopted.

  In addition, the termination resistance value setting device transmits a command to each node in parallel. For this reason, it is not necessary to repeat the operation of increasing and decreasing the resistance value of the variable resistor for each node, so that the processing is reduced.

  The terminal resistance value setting device according to each aspect of the present invention may be realized by a computer. In this case, the resistance device is realized by a computer by causing the computer to operate as each unit included in the resistance device. A control program for the resistance device and a computer-readable recording medium in which the control program is recorded also fall within the scope of the present invention.

  The present invention has an effect that it is possible to determine a resistance value of a termination resistor suitable for an actual communication environment.

It is a block diagram which shows the structure of the termination resistance value setting apparatus which concerns on Embodiment 1 of this invention. It is a flowchart which shows an example of the resistance value determination process of the variable termination resistance which concerns on Embodiment 1 of this invention. It is a block diagram which shows the structure of the termination resistance value setting apparatus which concerns on Embodiment 2 of this invention. It is a flowchart which shows an example of the resistance value determination process of the variable termination resistance which concerns on Embodiment 2 of this invention.

Embodiment 1
Embodiment 1 according to the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 is a block diagram showing a configuration of a termination resistance value setting device 2 according to the present embodiment. First, the outline of the communication network 50 according to the present embodiment will be described with reference to FIG. Here, in this embodiment, a case where the bus standard is a master-slave system will be described.

  As shown in FIG. 1, the communication network 50 includes a plurality of nodes 7 connected to the communication network 50, a termination resistance value setting device 2 that operates as a master device that transmits necessary data to the plurality of nodes 7, And a bus line 6 for connecting the node 7 and the termination resistance value setting device 2.

  The termination resistance value setting device 2 includes a termination resistance value setting unit 1 that determines a resistance value of a variable termination resistor 3 (described later), and an input / output unit 8 that transmits and receives data between the termination resistance value setting device 2 and each node 7. And is set as a master-slave master.

  The input / output unit 8 includes a variable termination resistor 3, a differential driver 4, and a differential receiver 5.

  The differential driver 4 uses two signal lines in response to a signal from a command transmission unit 11 (described later) of the termination resistance value setting unit 1 to transmit currents of opposite phases to each other and transmit with a potential difference between the signal lines. A command is transmitted to each node 7 according to the transmission format. The command may be any command as long as the node 7 returns a response signal, and may be, for example, ping.

  The differential receiver 5 synthesizes a response signal transmitted from each node 7 in the differential transmission format in response to the command transmitted by the differential driver 4 transmitted in the differential transmission format. The differential receiver 5 outputs the synthesized response signal to a response signal receiving unit 12 (described later) of the termination resistance value setting unit 1.

  The variable termination resistor 3 (variable resistor) is installed at the end of the communication network 50, and suppresses the influence of a reflected wave due to reflection of a signal transmitted through the communication network 50 at the end. Further, the resistance value of the variable termination resistor 3 changes under the control of the resistance value changing unit 13 (described later). The variable termination resistor 3 is a digital potentiometer in this embodiment. Although not shown, the digital potentiometer counts control signals transmitted from, for example, a resistance array in which a large number of resistors are connected in series, semiconductor switches connected to both ends of each resistor, and the resistance value changing unit 13. The counter includes a decoder that provides a value obtained by decoding the count value of the counter as a control signal for each semiconductor switch. In such a digital potentiometer, both ends of the resistor connected to the turned-on semiconductor switch are short-circuited and both ends of the resistor connected to the turned-off semiconductor switch are not short-circuited according to the decode value of the decoder. A resistance value corresponding to the total number of resistors connected to the switch is obtained.

  It is not always necessary to use a digital potentiometer as the variable termination resistor.

  As shown in FIG. 1, two variable termination resistors 3 are provided. One is connected to the positive output terminal of the differential driver 4 (positive input terminal of the differential receiver 5), and the other is connected to the differential driver 4. Connected to the negative output terminal (negative input terminal of the differential receiver 5). The resistance values of the two variable termination resistors 3 are the same, and when the resistance value is changed by the resistance value changing unit 13, the resistance values change simultaneously with the same amount of change.

  The node 7 is a terminal connected to the communication network 50, and is set as a master-slave slave. When the node 7 receives a command transmitted from the command transmission unit 11 of the termination resistance value setting unit 1, the node 7 transmits a response signal to the differential receiver 5 in a differential transmission format.

  The bus line 6 connects the termination resistance value setting device 2 and each node 7. The bus line 6 is a half-duplex bus having two transmission lines, transmits a command transmitted from the differential driver 4 to each node 7, and a response signal from each node 7 to the command. Is transmitted to the differential receiver 5.

  Next, the termination resistance value setting unit 1 will be described in detail.

  The termination resistance value setting unit 1 is a device that automatically sets the optimum resistance value of the variable termination resistor 3 in the communication network 50 by adjusting the resistance value of the variable termination resistor 3.

  As shown in FIG. 1, the termination resistance value setting unit 1 includes a control unit 10 and a storage unit 20.

  The control unit 10 performs control for setting the resistance value of the variable termination resistor 3 based on, for example, data stored in the storage unit 20. For this purpose, the control unit 10 includes a command transmission unit 11 that transmits a command to each node 7, a response signal reception unit 12 that receives a response signal from each node 7, and a resistor that changes the resistance value of the variable termination resistor 3. A value changing unit 13 and a resistance value determining unit 14 for determining the resistance value of the variable termination resistor 3 are provided.

  The command transmission unit 11 outputs a signal to the differential driver 4 based on a signal instructing transmission of a command from the resistance value changing unit 13 and transmits the command to a predetermined node 7. Further, the command transmission unit 11 shifts the transmission of the command to the next node 7 that has not yet been transmitted based on a signal from the resistance value changing unit 13 instructing the shift of the node 7.

  The response signal reception unit 12 (reception unit) receives the first reception signal or the second reception signal when the command transmission unit 11 receives the response signal of the node 7 for the command within a predetermined time after the command transmission unit 11 transmits the command. Output to the resistance value changing unit 13. Further, when the response signal receiving unit 12 does not receive the response signal for the command within a predetermined time after the command transmitting unit 11 transmits the command, the response signal receiving unit 12 determines the first non-received signal or the second received signal as a resistance value. Output to the changing unit 13. The predetermined time can be arbitrarily set.

  The resistance value changing unit 13 performs an operation of increasing the resistance value of the variable termination resistor 3 step by step every time the response signal receiving unit 12 receives the response signal (every time the first reception signal is output). Until the response termination signal is not received (until the first non-reception signal is output). On the other hand, the resistance value changing unit 13 performs an operation of decreasing the resistance value step by step every time the response signal receiving unit 12 receives the response signal (every time the second received signal is output). Until the signal is not received (until the second non-reception signal is output).

  For each node 7, the storage unit 20 is the previous variable termination resistor when the response signal receiving unit 12 no longer receives the response signal from each node 7 for the command transmitted from the command transmitting unit 11 within a predetermined time. The maximum value and the minimum value of the resistance value of 3 are stored.

  The resistance value determination unit 14 sets the smallest value among the maximum values of each node 7 stored in the storage unit 20 as the upper limit value, and is the largest of the minimum values of each node 7 stored in the storage unit 20. The larger value is set as the lower limit value, and the resistance value of the variable termination resistor 3 is determined between the upper limit value and the lower limit value.

  Next, the resistance value determination process of the termination resistance value setting unit 1 configured as described above will be described with reference to FIG. FIG. 2 is a flowchart illustrating an example of resistance value determination processing of the variable termination resistor 3 according to the first embodiment.

  The determination process of the resistance value by the termination resistance value setting unit 1 is executed after the communication network 50 is connected to the termination resistance value setting device 2 and each node 7 and before data communication is performed on the communication network 50.

  The above flow chart is applicable to the case where the communication network 50 uses the node 7 that can communicate when the resistance value of the variable termination resistor 3 is a value within the variable range. Therefore, before starting the processing of the flowchart, whether or not the response signal receiving unit 12 can receive a response signal to the command with respect to all values in the variable range of the resistance value of the variable termination resistor 3 for each node 7. The node 7 that is confirmed and cannot be received is excluded from the processing target.

  Specifically, every time the resistance value of the variable termination resistor 3 is changed stepwise from the smallest value in the variable range to the largest value, and every time the resistance value is changed stepwise, all nodes connected to the communication network 50 A command is transmitted to 7. Meanwhile, the node 7 for which the response signal receiving unit 12 cannot receive the response signal for the command is excluded from the processing target. In some cases, the node 7 that cannot receive the response signal is replaced and the above process is performed again.

  Here, when receiving a command from the command transmission unit 11, the node 7 transmits a response signal to the received command to the termination resistance value setting device 2. If the resistance value of the variable termination resistor 3 set at the time of command transmission is within the range of communicable resistance values, the communication network 50 functions normally, and the response signal receiver 12 receives the response transmitted from the node 7. Receive a signal. On the other hand, if the resistance value of the variable termination resistor 3 set at the time of command transmission is outside the range of resistance values that can be communicated, the communication network 50 transmits the reflected wave of the transmitted signal (command, response signal). In response, the response signal receiving unit 12 does not receive a response signal for the command.

  In addition, the response signal reception unit 12 receives a response signal from the node 7 for the command transmitted from the command transmission unit 11 within a predetermined time for the first time after the command transmission unit 11 starts transmitting the command to the predetermined node 7. When the signal is not received, the first non-reception signal is output to the resistance value changing unit 13. The response signal receiving unit 12 receives the command transmitted from the command transmitting unit 11 from the node 7 until the command transmitting unit 11 outputs the first non-received signal after the command transmitting unit 11 starts transmitting the command to the node 7. When the response signal is received within a predetermined time, the first reception signal is output to the resistance value changing unit 13.

  The response signal receiving unit 12 outputs the first non-reception signal to the resistance value changing unit 13 at the node 7, and then the response signal from the node 7 to the command transmitted from the command transmitting unit 11 is again received for a predetermined time. The second non-reception signal is output to the resistance value changing unit 13 when the signal is not received within. The response signal receiving unit 12 outputs the first non-received signal to the resistance value changing unit 13 and outputs the second non-received signal from the node 7 corresponding to the command transmitted from the command transmitting unit 11. When the response signal is received within a predetermined time, the second reception signal is output to the resistance value changing unit 13.

  In the process of the flowchart shown in FIG. 2, the resistance value changing unit 13 first sets the resistance value of the variable termination resistor 3 to an initial value (a preset value of the counter) (S1). The initial value of the resistance value of the variable termination resistor 3 can be arbitrarily set. For example, a resistance value that has been adopted in the conventional standard may be used. Thereafter, the command transmission unit 11 transmits a command to a predetermined node 7, that is, one of the plurality of nodes 7 (S2), and the resistance value changing unit 13 transmits the command from the command transmission unit 11 to the node 7. Then, it is determined whether or not the response signal receiving unit 12 has received a response signal to the command within a predetermined time (S3).

  In S3, when the response signal receiving unit 12 receives a response signal to the command within a predetermined time (YES in S3), that is, when the resistance value changing unit 13 receives the first received signal from the response signal receiving unit 12. The resistance value changing unit 13 increases the resistance value of the variable termination resistor 3 by a certain amount, and the command transmitting unit 11 transmits a command (S4). Specifically, the resistance value changing unit 13 outputs at least one pulse signal to increase the resistance value by a certain amount, and gives an up-count signal that counts up to the counter at the first increase. When the counter of the variable termination resistor 3 up-counts the applied pulse signal from the preset value, the decode value of the decoder changes some of the semiconductor switches that are turned on to the off state according to the count value of the counter. Thereby, the number of resistors connected in series in the resistor array increases, and the resistance value of the variable termination resistor 3 increases. Further, the resistance value changing unit 13 outputs a signal instructing the node 7 to transmit a command to the command transmitting unit 11, and when the command transmitting unit 11 receives the signal from the resistance value changing unit 13, the node 7 Send the command again.

  Thereafter, the resistance value changing unit 13 determines whether or not the response signal receiving unit 12 has received a response signal to the command within a predetermined time (S5).

  In S5, when the response signal receiving unit 12 does not receive a response signal for the command within a predetermined time (NO in S5), that is, the resistance value changing unit 13 receives the first non-received signal from the response signal receiving unit 12. When received, the resistance value changing unit 13 causes the storage unit 20 to store the previous resistance value of the variable termination resistor 3 as the maximum value of the resistance value range of the variable termination resistor 3 that can communicate with the node 7. (S6). Thereafter, the resistance value changing unit 13 returns the resistance value of the variable termination resistor 3 to the initial value (S7). Of course, the initial value in S7 is an initial value at which a response signal is received in response to command transmission to the node, that is, an initial value at which a response signal is received in S3.

  Subsequently, the resistance value changing unit 13 decreases the resistance value of the variable termination resistor 3 by a certain amount, and the command transmitting unit 11 transmits a command (S9). Specifically, the resistance value changing unit 13 outputs at least one pulse signal to decrease the resistance value by a certain amount, and gives a down-count signal that counts down to the counter when the resistance value is first decreased. When the counter of the variable termination resistor 3 counts down the applied pulse signal from the preset value, the decode value of the decoder changes some of the semiconductor switches that are turned off to the on state in accordance with the count value of the counter. As a result, the number of resistors connected in series in the resistor array decreases, and the resistance value of the variable termination resistor 3 decreases. Furthermore, the resistance value changing unit 13 outputs a signal instructing the node 7 to transmit a command to the command transmitting unit 11. When the command transmitting unit 11 receives the signal from the resistance value changing unit 13, Send the command to 7 again.

  Thereafter, the resistance value changing unit 13 determines whether or not the response signal receiving unit 12 has received a response signal to the command within a predetermined time (S10).

  In S10, when the response signal receiving unit 12 does not receive the response signal for the command within a predetermined time (NO in S10), that is, the resistance value changing unit 13 receives the second non-received signal from the response signal receiving unit 12. When received, the resistance value changing unit 13 causes the storage unit 20 to store the previous resistance value of the variable termination resistor 3 as the minimum value of the resistance value range of the variable termination resistor 3 that can communicate with the node 7. (S11).

  Next, the resistance value changing unit 13 determines whether or not the storage of the maximum value and the minimum value is finished for all the nodes 7 connected to the communication network 50 (S12). In the determination, for example, the resistance value changing unit 13 determines the end if the second non-received signal is from the last node 7, and does not end unless the second non-received signal is the last one. judge.

  In S12, when the storage of the maximum value and the minimum value has been completed for all the nodes 7 (YES in S12), the resistance value changing unit 13 ends the command transmission to all the nodes 7 to the resistance value determining unit 14. A signal indicating is output. When the resistance value determining unit 14 receives the signal from the resistance value changing unit 13, the node 7 that has obtained a minimum value greater than the smallest value (upper limit value) of the maximum resistance values for each node 7. Alternatively, it is determined whether or not there is a node 7 having a maximum value smaller than the largest value (lower limit value) of the minimum resistance values for each node 7 (S14). In this determination, the resistance value determination unit 14 refers to the maximum value and the minimum value of the resistance value for each node 7 stored in the storage unit 20, and determines the resistance value for each node 7. The upper limit value and the lower limit value are stored in the storage unit 20 with the smallest value as the upper limit value and the largest value among the minimum resistance values for each node 7 as the lower limit value.

  When there is no node 7 that has obtained a minimum value that is greater than the upper limit value or no node 7 that has obtained a maximum value that is less than the upper limit value (NO in S14), the minimum value and the lower limit value that are less than or equal to the upper limit value are obtained from all the nodes 7. The maximum value is obtained. In this case, the resistance value determining unit 14 refers to the upper limit value and the lower limit value stored in the storage unit 20, and determines the resistance value of the variable termination resistor 3 between the upper limit value and the lower limit value (S15). . Moreover, it is preferable that the said resistance value determination part 14 determines the median value of an upper limit value and a lower limit value as resistance value. When the resistance value determination unit 14 gives the determined resistance value to the counter of the variable termination resistor 3 as a preset value, the counter loads the preset value and supplies it to the decoder. As a result, the semiconductor switch is turned on in accordance with the decode value of the decoder, and the resistor array is connected in series with the number of resistors corresponding to the determined resistance value.

  In S3, when the response signal receiving unit 12 does not receive the response signal for the command within a predetermined time (NO in S3), that is, the resistance value changing unit 13 receives the first non-received signal from the response signal receiving unit 12. When received, the resistance value changing unit 13 randomly changes the resistance value (initial value) of the variable termination resistor 3 (S16), and repeats the processes of S1 to S3 and S16 until a response signal is received in S3.

  In S5, when the response signal receiving unit 12 receives a response signal to the command within a predetermined time (YES in S5), that is, when the resistance value changing unit 13 receives the first received signal from the response signal receiving unit 12. The resistance value changing unit 13 further increases the resistance value of the variable termination resistor 3 by a certain amount (S4). The processes of S4 and S5 are repeated until the response signal receiving unit 12 does not receive a response signal for the command within a predetermined time in S5. In other words, the processes of S4 and S5 are repeated each time the first received signal is received until the resistance value changing unit 13 receives the first non-received signal from the response signal receiving unit 12. Meanwhile, whenever the resistance value changing unit 13 receives the first reception signal from the response signal receiving unit 12, the resistance value changing unit 13 gradually increases the resistance value of the variable termination resistor 3 at a constant rate.

  In S10, when the response signal receiving unit 12 receives a response signal to the command within a predetermined time (YES in S10), that is, when the resistance value changing unit 13 receives the second received signal from the response signal receiving unit 12. The resistance value changing unit 13 further decreases the resistance value of the variable termination resistor 3 by a certain amount (S9). The processes of S9 and S10 are repeated until the response signal receiving unit 12 does not receive a response signal for the command within a predetermined time in S10. In other words, the processes of S9 and S10 are repeated each time the second received signal is received until the resistance value changing unit 13 receives the second non-received signal from the response signal receiving unit 12. Meanwhile, whenever the resistance value changing unit 13 receives the second received signal from the response signal receiving unit 12, the resistance value changing unit 13 gradually decreases the resistance value of the variable termination resistor 3 at a constant rate.

  In S12, when the storage of the maximum value and the minimum value is not completed for all the nodes 7 (NO in S12), the resistance value changing unit 13 outputs a signal instructing the command transmitting unit 11 to shift to the node 7. When the command transmission unit 11 receives the signal, the command transmission unit 11 shifts the command transmission to the next node 7 that has not yet transmitted the command, that is, the node 7 that has not finished storing the maximum value and the minimum value ( S13). Thereafter, the process returns to S <b> 1, and the processes of S <b> 1 to S <b> 13 are repeated until the maximum value and the minimum value of all the nodes 7 connected to the communication network 50 are stored in the storage unit 20.

  In S14, when there is a node 7 having a minimum value greater than the upper limit value or when there is a node 7 having a maximum value smaller than the lower limit value (YES in S14), the communicable range of the node 7 is other than It does not overlap with the communicable range (common communicable range) of node 7 (node 7 from which the minimum value equal to or lower than the upper limit value and the maximum value equal to or higher than the lower limit value) is obtained. Therefore, it is necessary to adjust so that there is no communicable range that does not overlap between the nodes 7. In this case, the resistance value determination unit 14 notifies the user that there is a node 7 having a communicable range that does not overlap with the common communicable range, prompts the user to make adjustments, and checks whether the adjustment has been performed. (S17). Specifically, the adjustment is to change the wiring route to the node 7, change the wiring member, or exclude the node 7 from the communication network 50. When the resistance value determining unit 14 confirms that the above adjustment has been made by a user input or the like (YES in S17), the resistance value determining unit 14 notifies the resistance value changing unit 13 to start the process again from S1. If the resistance value determination unit 14 cannot confirm that the adjustment has been made (NO in S17), the resistance value determination unit 14 waits until the adjustment can be confirmed.

  In a predetermined node 7, the response signal receiving unit 12 receives a response signal corresponding to the command transmitted from the command transmitting unit 11 within a predetermined time with respect to all resistance values in the variable range of the variable termination resistor 3. There are cases. At this time, the variable termination resistor 3 can be said to be suitable for the communication environment of the node 7 no matter what resistance value is adopted within the variable range. You may move to the next node without detecting the value. When there is a node 7 for which the maximum value and the minimum value are not detected, when determining the upper limit value and the lower limit value in S14, the maximum value of each node 7 stored in the storage unit 20 other than the node 7 and Determine the upper and lower limits from the minimum.

  In all the nodes 7 connected to the communication network 50, the response signal receiving unit 12 sends the response signal corresponding to the command transmitted from the command transmitting unit 11 to all the resistance values in the variable range of the variable termination resistor 3. The resistance value determining unit 14 preferably determines the intermediate value of the variable range of the variable termination resistor 3 as the resistance value, but if the value is within the variable range, the other value is used. May be.

  In the present embodiment, the communication network 50 has been described as a master-slave system, but the present invention is not limited to the above. For example, the termination resistance value setting unit 1 can be applied even when the communication network 50 sets the node 7 as a master. As described above, the termination resistance value setting unit 1 can be applied to both cases where the communication network 50 is a master-slave system or a multi-master system. However, the device including the termination resistance value setting unit 1 is a master (terminating resistance value setting). It must be a device 2).

  In the present embodiment in which the communication network 50 is a master-slave system, the maximum value and the minimum value of the communicable range of the resistance value of the variable termination resistor 3 at each node 7 are determined depending on whether the response signal is received by the response signal receiving unit 12. get. On the other hand, when the communication network 50 is a multi-master system, the maximum value and the minimum value of the communicable range of the resistance value of the variable termination resistor 3 at each node 7 depending on the presence or absence of a communication error in the response signal receiving unit 12. To get. Thus, it is desirable to change the resistance value determination processing method according to the bus standard or protocol to be used.

  As described above, the termination resistance value setting unit 1 performs the operation of increasing the resistance value of the variable termination resistor 3 step by step every time the response signal receiving unit 12 receives the response signal. The first control for causing the variable termination resistor 3 to continue within the receivable range and the operation of decreasing the resistance value of the variable termination resistor 3 step by step each time the response signal receiving unit 12 receives the response signal. The second control for causing the variable termination resistor 3 to continue within the range in which the response signal can be received by the node 12 is performed for each node 7 so that one of the second controls comes first. Further, by the operation of increasing or decreasing the resistance value of the variable termination resistor 3 by the first control and the second control, the maximum value and the minimum value of the resistance value of the variable termination resistor 3 at each node 7 capable of receiving the response signal are obtained. The data is stored in the storage unit 20 (the maximum value and the minimum value of the resistance values are not stored in the storage unit 20 for the node 7 that can be received with respect to all resistance values in the variable range of the variable termination resistor 3). That is, when the resistance value changing unit 13 receives the first non-reception signal from the response signal receiving unit 12, the resistance value changing unit 13 determines the maximum value of the resistance value range of the variable termination resistor 3 that can communicate at the node 7. The resistance value of the previous variable termination resistor 3 is stored in the storage unit 20 (if the resistance value matches the maximum value of the variable range of the variable termination resistor 3, the resistance value is not stored in the storage unit 20. ). When the resistance value changing unit 13 receives the second non-reception signal from the response signal receiving unit 12, the resistance value changing unit 13 is the minimum value of the resistance value range of the variable termination resistor 3 that can communicate with the node 7. The resistance value of the previous variable termination resistor 3 is stored in the storage unit 20 (if the resistance value matches the minimum value of the variable range of the variable termination resistor 3, the resistance value is not stored in the storage unit 20. ). Therefore, in a state in which the communication network 50 is actually constructed, each node in which the resistance value that does not match the communication environment is included in the variable range of the resistance value of the variable termination resistor 3 and the communicable ranges overlap. 7, it is possible to grasp the maximum value and the minimum value of the resistance value of the variable termination resistor 3 that can perform communication normally.

  In addition, the termination resistance value setting unit 1 determines the resistance value of the variable termination resistor 3 between the smallest value (upper limit value) of the maximum resistance value of the variable termination resistor 3 and the largest value (lower limit value) of the minimum value. To decide. Therefore, the resistance value of the variable termination resistor 3 can be determined within a range in which each node 7 connected to the communication network 50 can normally communicate. As a result, the resistance value of the variable termination resistor 3 suitable for the actual communication environment can be determined. Thereby, it is possible to prevent a communication error due to the fact that the resistance value of the termination resistor is not compatible with the communication network 50, as in the case where the resistance value of the conventionally determined termination resistor is adopted.

  Further, the termination resistance value setting unit 1 sets the median value between the upper limit value and the lower limit value stored in the storage unit 20 as the resistance value of the variable termination resistor 3. For this reason, since there is a margin in the range in which normal communication can be performed in the communication network 50, it is possible to cope with changes in the communication environment due to external factors and the like.

[Embodiment 2]
Embodiment 2 according to the present invention will be described below with reference to FIGS. 3 and 4. In addition, the same code | symbol is attached | subjected to each member which is common in Embodiment 1 mentioned above, and detailed description is abbreviate | omitted. FIG. 3 is a block diagram illustrating a configuration of the termination resistance value setting unit 1A according to the second embodiment of the present invention.

  This embodiment is different from Embodiment 1 in the method of transmitting commands and determining the maximum value and the minimum value of the resistance value of the variable termination resistor 3. Specifically, in the first embodiment, a command is transmitted to each node 7 connected to the communication network 50, and the maximum value and the minimum value of the resistance value of the node 7 that can receive the response signal are stored in the storage unit 20. Yes. On the other hand, in this embodiment, transmission of a command to each node 7 connected to the communication network 50 and storage of the resistance value of each node 7 capable of receiving a response signal in the storage unit 20 are performed in parallel.

  As shown in FIG. 3, the termination resistance value setting device 2 includes a termination resistance value setting unit 1A instead of the termination resistance value setting unit 1 in the termination resistance value setting device 2 shown in FIG. Includes a control unit 10 </ b> A and a storage unit 20.

  The control unit 10A includes a command transmission unit 11 that transmits a command to each node 7, a response signal reception unit 16 that receives a response signal from each node 7, and a resistance value change unit that changes the resistance value of the variable termination resistor 3. 15 and a resistance value determination unit 14 that determines the resistance value of the variable termination resistor 3.

  When the response signal receiving unit 16 (receiving unit) receives the response signal of the node 7 for the command within a predetermined time after the command transmitting unit 11 transmits the command, the node 7 that has received the response signal within the predetermined time. Is output to the resistance value changing unit 15. The predetermined time can be arbitrarily set, but at least the time from when the command is transmitted from the command transmission unit 11 until it is received by the node 7, the response signal is transmitted from the node after the command is received by the node 7. And the total time from when the response signal is transmitted from the node 7 until it is received by the response signal receiving unit 12 is set.

  The resistance value changing unit 15 performs an operation of increasing the resistance value of the variable termination resistor 3 step by step every time a predetermined time has elapsed since the command transmission unit 11 transmitted the command. The variable termination resistor 3 is continued until the maximum value is reached. Further, the resistance value changing unit 15 performs an operation of decreasing the resistance value of the variable termination resistor 3 step by step every time a certain time has elapsed since the command transmission unit 11 transmitted the command. Until the minimum value of the variable range is reached.

  The storage unit 20 stores the resistance value when the command is transmitted from the command transmission unit 11 and the node 7 at which the response signal reception unit 16 has received the response signal in association with the command.

  Next, the resistance value determination process of the termination resistance value setting unit 1 configured as described above will be described with reference to FIG. FIG. 4 is a flowchart illustrating an example of resistance value determination processing for the variable termination resistor 3 according to the second embodiment.

  As shown in FIG. 4, first, the resistance value changing unit 15 sets the resistance value of the variable termination resistor 3 to an initial value (a preset value of the counter) (S21). The initial value of the resistance value of the variable termination resistor 3 can be arbitrarily set. For example, a resistance value that has been adopted in the conventional standard may be used. Thereafter, the command transmission unit 11 transmits the command to all the nodes 7 connected to the communication network 50 (S22). Based on the received signal from the response signal receiving unit 16, the resistance value changing unit 15 receives the response signal for the command within a predetermined time after the command is transmitted from the command transmitting unit 11 to each node 7. The node 7 that received the message is confirmed (S23). The resistance value changing unit 15 causes the storage unit 20 to store the resistance value when the command is transmitted and the node 7 that has confirmed the reception of the response signal. The resistance value changing unit 15 does not store the node 7 and the resistance value in the storage unit 20 for the node 7 that has not received the response signal. The process of not storing the node 7 and the resistance value that have not received the response signal in the storage unit 20 is performed in the same manner in the confirmation (S26, S30) of the node 7 that has received the response signal.

  After a predetermined time has elapsed since the command transmission unit 11 transmitted the command, the resistance value changing unit 15 increases the resistance value of the variable termination resistor 3 by a certain amount (S24), and instructs all nodes 7 to transmit the command. The signal is output to the command transmission unit 11. Here, the predetermined time may be any time as long as it is equal to or longer than the predetermined time.

  When receiving the signal from the resistance value changing unit 15, the command transmitting unit 11 transmits the command to all the nodes 7 again (S25). Based on the received signal from the response signal receiving unit 16, the resistance value changing unit 15 receives the response signal receiving unit within a predetermined time after the command is transmitted from the command transmitting unit 11 to each node 7 with the increased resistance value. 16 confirms the node 7 that has received the response signal to the command (S26). Further, the resistance value changing unit 15 causes the storage unit 20 to store the resistance value when the command is transmitted and the node 7 that has confirmed reception of the response signal.

  Next, the resistance value changing unit 15 determines whether or not the resistance value of the variable termination resistor 3 has been increased to the largest value in the variable range (S27).

  When the resistance value increases to the largest value in the variable range of the variable termination resistor 3 (YES in S27), the resistance value changing unit 15 decreases the resistance value of the variable termination resistor 3 by a certain amount (S28). The resistance value changing unit 15 outputs a signal instructing all nodes 7 to transmit a command to the command transmitting unit 11. When the command transmission unit 11 receives the signal from the resistance value changing unit 15, the command transmission unit 11 transmits the command to all the nodes 7 again (S29). Based on the received signal from the response signal receiving unit 16, the resistance value changing unit 15 has a response value receiving unit within a predetermined time after the command is transmitted from the command transmitting unit 11 to each node 7 with the reduced resistance value. 16 confirms the node 7 that has received the response signal to the command (S30). In addition, the resistance value changing unit 15 causes the storage unit 20 to store the resistance value when the command is transmitted and the node 7 that has confirmed reception of the response signal.

  It should be noted that it is preferable that a further step is provided between S27 and S28 so that the process of S28 is performed after the resistance value is set to the initial value in S21.

  Next, the resistance value changing unit 15 determines whether or not the resistance value of the variable termination resistor 3 has been reduced to the smallest value in the variable range (S31). When the resistance value decreases to the smallest value in the variable range of the variable termination resistor 3 (YES in S31), the resistance value changing unit 15 sends a signal indicating the end of command transmission to all the nodes 7 to the resistance value determining unit 14. Is output. By performing the processing of S21 to S31, the resistance value range of the variable termination resistor 3 in which each node 7 can receive the response signal can be found by referring to the resistance value stored in the storage unit 20.

  When the resistance value determining unit 14 receives the signal from the resistance value changing unit 15, the resistance value determining unit 14 determines the value of each node 7 out of the resistance value range of the variable termination resistor 3 communicable in each node 7 stored in the storage unit 20. The maximum value smaller than the largest value (lower limit value) of the minimum values of the resistance values for the node 7 or each node 7 at which the smallest value larger than the smallest value (upper limit value) of the maximum resistance values is obtained. It is determined whether or not there is a node 7 that has been obtained (S32). In this determination, the resistance value determination unit 14 refers to the maximum value and the minimum value of the resistance value for each node 7 stored in the storage unit 20, and determines the resistance value for each node 7. The upper limit value and the lower limit value are stored in the storage unit 20 with the smallest value as the upper limit value and the largest value among the minimum resistance values for each node 7 as the lower limit value.

  When there is no node 7 that has obtained a minimum value that is greater than each upper limit value or no node 7 that has obtained a maximum value that is less than the upper limit value (NO in S32), the minimum value and the lower limit that are less than or equal to the upper limit value are obtained from all nodes 7. The maximum value that is greater than or equal to the value is obtained. In this case, the resistance value determination unit 14 refers to the upper limit value and the lower limit value stored in the storage unit 20, and determines the resistance value of the variable termination resistor 3 between the upper limit value and the lower limit value (S33). . Moreover, it is preferable that the said resistance value determination part 14 determines the median value of an upper limit value and a lower limit value as resistance value.

  In S27, when the resistance value has not increased to the maximum value in the variable range of the variable termination resistor 3 (NO in S27), the resistance value changing unit 15 further increases the resistance value of the variable termination resistor 3 by a certain amount ( S24). The processing of S24 to S27 is repeated until the resistance value of the variable termination resistor 3 increases to the largest value in the variable range in S27. In the meantime, the resistance value changing unit 15 increases the resistance value of the variable termination resistor 3 stepwise at a constant rate every time a certain time has elapsed since the command was transmitted from the command transmission unit 11. For each increased resistance value, the resistance value changing unit 15 causes the storage unit 20 to store the node 7 that has received the response signal for the command within a predetermined time based on the received signal from the response signal receiving unit 16 and the resistance value. .

  In S31, when the resistance value has not decreased to the smallest value of the variable range of the variable termination resistor 3 (NO in S31), the resistance value changing unit 15 further decreases the resistance value of the variable termination resistor 3 by a certain amount ( S28). The processing of S28 to S31 is repeated until the resistance value of the variable termination resistor 3 is decreased to the smallest value in the variable range in S31. In the meantime, the resistance value changing unit 15 decreases the resistance value of the variable termination resistor 3 step by step at a constant rate every time a certain time has elapsed since the command was transmitted from the command transmitting unit 11. The resistance value changing unit 15 causes the storage unit 20 to store the node 7 that has received the response signal to the command within a predetermined time based on the received signal from the response signal receiving unit 16 for each decreased resistance value and the resistance value.

  In S32, when there is a node 7 that has obtained a minimum value that is greater than the upper limit value or there is a node 7 that has obtained a maximum value that is less than the lower limit value (YES in S32), the resistance value determining unit 14 Similar to S17 shown, the user is informed that there is a node 7 having a communicable range that does not overlap with the common communicable range, prompts the user to make an adjustment, and confirms whether or not the adjustment has been performed (S34). When the resistance value determination unit 14 confirms that the above adjustment has been made by a user input or the like (YES in S34), the resistance value determination unit 14 notifies the resistance value change unit 15 to start the process again from S21. If the resistance value determination unit 14 cannot confirm that the adjustment has been performed (NO in S34), the resistance value determination unit 14 waits until the adjustment can be confirmed.

  In the predetermined node 7, the response signal receiving unit 16 receives the response signal corresponding to the command transmitted from the command transmitting unit 11 within a predetermined time with respect to all resistance values in the variable range of the variable termination resistor 3. There are cases. At this time, the variable termination resistor 3 can be said to be suitable for the communication environment of the node 7 no matter what resistance value is adopted within the variable range. The value need not be detected. When the maximum value and the minimum value are not detected in the predetermined node 7, when determining the upper limit value and the lower limit value in S32, the maximum value and the minimum value of each node 7 stored in the storage unit 20 other than the node 7 Determine the upper and lower limits from

  As described above, the termination resistance value setting unit 1A performs the operation of increasing the resistance value of the variable termination resistor 3 step by step every time the response signal receiving unit 16 confirms whether or not the response signal is received. First control for causing the variable termination resistor 3 to continue to receive the response signal within the range in which the response signal 16 can be received, and the resistance value of the variable termination resistor 3 step by step each time the response signal receiving unit 16 confirms whether or not the response signal is received. The second control that causes the variable termination resistor 3 to continue the operation for decreasing the response signal within the range in which the response signal receiving unit 16 can receive the response signal is performed in parallel for all the nodes 7 so that either one comes first. . Further, the resistance value of the variable termination resistor 3 at each node 7 capable of receiving the response signal is obtained and stored in the storage unit 20 by the operation of increasing or decreasing the resistance value of the variable termination resistor 3 by the first control and the second control. Therefore, in the state where the communication network 50 is actually constructed, it is possible to grasp the resistance value of the variable termination resistor 3 at which communication can be normally performed at each node 7 where the communicable ranges overlap.

  Further, the termination resistance value setting unit 1 </ b> A has a resistance value of the variable termination resistor 3 between the smallest value (upper limit value) of the maximum resistance value of the variable termination resistor 3 and the largest value (lower limit value) of the minimum value. To decide. Therefore, the resistance value of the variable termination resistor 3 can be determined within a range in which each node 7 connected to the communication network 50 can normally communicate. As a result, the resistance value of the variable termination resistor 3 suitable for the actual communication environment can be determined. Thereby, it is possible to prevent a communication error due to the fact that the resistance value of the termination resistor is not compatible with the communication network 50, as in the case where the resistance value of the conventionally determined termination resistor is adopted.

  Further, the termination resistance value setting unit 1A performs transmission of a command to each node 7, confirmation of reception of the command of each node 7, and increase and decrease of the resistance value of the variable termination resistor 3 at a time. For this reason, since it is not necessary to repeat the operation of increasing and decreasing the resistance value of the variable termination resistor 3 for each node 7, the processing is reduced as compared with the termination resistance value setting unit 1 of the first embodiment.

  Since the termination resistance value setting unit 1A stores the resistance value when each node 7 has received the command in the storage unit 20, the resistance value of the variable termination resistor 3 in the variable range is stored from the stored resistance value. For all values, it can be seen whether or not each node 7 has received a response signal to the command. Therefore, as in the termination resistance value setting unit 1 of the first embodiment, it is confirmed for each node 7 whether a response signal to the command can be received for all values in the variable range of the resistance value of the variable termination resistor 3. There is no need to do.

[Example of software implementation]
The control blocks of the termination resistance value setting units 1 and 1A (in particular, the command transmission unit 11, the response signal reception unit 12, the resistance value change unit 13, the resistance value determination unit 14, the resistance value change unit 15, and the response signal reception unit 16) Alternatively, it may be realized by a logic circuit (hardware) formed in an integrated circuit (IC chip) or the like, or may be realized by software using a CPU (Central Processing Unit).

  In the latter case, the termination resistance value setting units 1 and 1A include a CPU that executes instructions of a program that is software that realizes each function, and a ROM (Read Only Memory) in which the program and various data are recorded so as to be readable by the CPU. ) Or a storage device (these are referred to as “recording media”), a RAM (Random Access Memory) for expanding the program, and the like. Then, the object of the present invention is achieved by the CPU reading the program from the recording medium and executing the program. As the recording medium, a “non-temporary tangible medium” (such as a semiconductor memory) can be used. The program may be supplied to the computer via an arbitrary transmission medium (such as a communication network or a broadcast wave) that can transmit the program. The present invention can also be realized in the form of a data signal embedded in a carrier wave in which the program is embodied by electronic transmission.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  The present invention can be used for adjusting a variable resistance value.

1.1A Termination resistance value setting section 3 Variable termination resistance (variable resistance)
4 Differential Driver 5 Differential Receiver 6 Bus Line 7 Node 11 Command Transmitter (Transmitter)
12 Response signal receiver (receiver)
13 resistance value changing unit 14 resistance value determining unit 15 resistance value changing unit 16 response signal receiving unit (receiving unit)
20 storage unit 50 communication network (network)

Claims (2)

A variable resistor installed in a network to which multiple nodes are connected;
A resistance value determining unit for determining a resistance value of the variable resistor;
A transmitter for transmitting a command to each of the above nodes;
A receiver that receives a response signal from each of the nodes in response to the command transmitted by the transmitter;
A first control for causing the variable resistor to continue the operation of increasing the resistance value step by step each time the receiving unit receives the response signal in a range in which the receiving unit can receive the response signal; One of the first control and the second control for causing the receiving unit to continue the operation of decreasing the resistance value stepwise every time the response signal is received within a range in which the reception unit can receive the response signal. And a resistance value changing unit for each of the nodes,
A storage unit that stores a maximum value and a minimum value of the resistance value when the response signal is receivable for each of the nodes;
The resistance value determination unit sets the smallest value among the maximum values for each of the nodes stored in the storage unit as an upper limit value and the minimum value for each of the nodes stored in the storage unit And the resistance between the upper limit value and the lower limit value for the node at which the minimum value equal to or lower than the upper limit value and the maximum value equal to or higher than the lower limit value are obtained. A terminal resistance value setting device for determining a value. A variable resistor installed at the end of a network to which multiple nodes are connected;
A resistance value determining unit for determining a resistance value of the variable resistor;
A transmitter that sends commands to each of the above nodes at once;
A receiver that receives a response signal from each of the nodes in response to the command transmitted by the transmitter;
A first control for causing the variable resistor to continue the operation of increasing the resistance value step by step within a variable range of the resistance value of the variable resistor every time a predetermined time elapses from the transmission of the command; The second control for causing the variable resistor to continue the operation of decreasing the resistance value step by step in the variable range of the resistance value of the variable resistor as each time elapses is performed first, and each of the above-mentioned A resistance value changing unit for the nodes in parallel;
A storage unit that stores, for each of the nodes, the resistance value when the response signal is receivable;
The resistance value determining unit sets the smallest value among the maximum values of the resistance values for each of the nodes stored in the storage unit as an upper limit value, and for each of the nodes stored in the storage unit. The maximum value among the minimum values of the resistance value is set as a lower limit value, and the upper limit value and the lower limit value of the node at which the minimum value that is not more than the upper limit value and the maximum value that is not less than the lower limit value are obtained. The terminal resistance value setting device, wherein the resistance value is determined between

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