JP3581283B2 - Communication device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a communication device that is connected to another communication device via a communication connection unit and performs communication with the connected communication device by a digital transmission method.
[0002]
[Prior art]
Conventionally, as this type of communication device, for example, there is an industrial temperature controller. This industrial temperature controller is provided with a terminal block, a connector, a stereo pin jack, and the like as a connection part for communication, and is connected to communication equipment such as a controller for control via this connection part for communication.
[0003]
FIG. 4 shows the connection between the industrial temperature controller and the controller for control. In the figure, 1 is an industrial temperature controller, 1-1 is a communication connection (digital communication connection) in the industrial temperature controller 1, and 1-2 is a CPU (central processing unit) built in the industrial temperature controller 1. processor), 2 control controller 3 is a cable communication which connects the industrial temperature controller 1 and the control controller 2.
[0004]
Communication is performed between the industrial temperature controller 1 and the controller 2 by a digital transmission method. Further, the industrial temperature controller 1 has a function of detecting whether or not the control controller 2 is connected and automatically switching its operation. That is, the industrial temperature controller 1 sets the communication state when the connection of the control controller 2 is detected, and sets the communication state when the connection is not detected, and performs the operation according to each state. .
[0005]
As a method for detecting the presence or absence of connection of the control controller 2 in the industrial temperature controller 1, there are the following methods (1) and (2).
(1) Upon receiving a communication command from the control controller 2, the presence or absence of connection of the control controller 2 is detected.
{Circle around (2)} A mechanical switch is provided in the communication connection unit 1-1, and the presence / absence of connection of the control controller 2 is detected from on / off of the mechanical switch.
[0006]
[Problems to be solved by the invention]
However, according to the method (1) described above, a communication command must be sent from the control controller 2 to the industrial temperature controller 1, and after the communication state is set, the communication cable 1-1 is connected to the communication cable 1-1. When 3 is off, it is impossible to return to the non-communication state. Moreover, there was a possibility of erroneous detection due to the influence of electromagnetic noise.
[0007]
Further, according to the method (2) described above, when the corrosion contact failure of the communication connection portion 1-1 occurs, the on / off state of the mechanical switch is fixed in the stereo pin jack or the like, and the control controller 2 There is a case where the communication state is set despite not being connected, or the communication state is not set even though the control controller 2 is connected. Moreover, it has been difficult to improve this poor contact state by an external action. Further, a detection signal line is required separately from the transmission / reception line, and there is a problem that an extra input port of the CPU 1-2 in the industrial temperature controller 1 is necessary.
[0008]
The present applicant previously proposed a communication apparatus as disclosed in Japanese Utility Model Laid-Open No. 63-129351. FIG. 5 shows a circuit diagram disclosed in Japanese Utility Model Laid-Open No. 63-129351. In the figure, 4 is a two-wire transmission line, 5 is a power source, 6 is a transmitter that receives power supplied from the power source 5 and sends a current signal as analog data in the range of 4 to 20 mA, and RL is a voltage of the current signal. A resistor 7 for taking out as a signal is a portable communication device. The portable communication device 7 is optionally connected to the two-wire transmission line 4 via terminals A and B, and communicates with the transmitter 6 via the two-wire transmission line 4. The portable communication device 7 has a connection determination circuit 71. The connection determination circuit 71 includes a comparator 711, a power supply 712, and a detection resistor Rp.
[0009]
In FIG. 5, the current I (4 mA) flows through the two-wire transmission line 4 even when there is no signal. For this reason, if the portable communication device 7 is connected to the two-wire transmission line 4, a voltage V is generated across the detection resistor Rp, and the comparator 711 outputs an “H” level. When the portable communication device 7 is disconnected from the two-wire transmission line 4, the voltage across the detection resistor Rp becomes zero, and the comparator 711 outputs the “L” level.
[0010]
If the connection judgment circuit 71 in the portable communication device 7 disclosed in Japanese Utility Model Publication No. 63-129351 is provided in the industrial temperature controller 1 shown in FIG. However, the signal transmission method between the industrial temperature controller 1 and the control controller 2 is not an analog transmission method (4 to 20 mA) but a digital transmission method (“H” / “L” level). In the digital transmission system, the voltage of the signal line is zero when there is no signal. For this reason, even if the connection determination circuit 71 is provided in the industrial temperature controller 1, it cannot be distinguished whether the voltage is zero due to no signal or whether the voltage is zero because the connection of the control controller 2 is disconnected. The connection / disconnection of the control controller 2 cannot be detected.
[0011]
The present invention has been made to solve such problems, and an object of the present invention is to easily and reliably detect a connection state with another communication device in a communication apparatus that performs communication by a digital transmission method.
[0012]
[Means for Solving the Problems]
In order to achieve such an object, the present invention provides communication when an output port is switched to an input port when communication data is not transmitted, in combination with an external circuit on the side of a communication device connected via a communication connection unit. An internal circuit is provided that sets the voltage value of the transmission line for communication data to the device to “H” level when the communication device is connected and “L” level when the communication device is not connected, and periodically sets the voltage value of the transmission line when communication data is not transmitted. By checking automatically, the presence or absence of connection of the communication device to the communication connection unit is detected. In addition, a communication system on the communication driver side is provided separately from the communication system on the communication connection side, and the communication device is connected to the communication connection unit based on the detection result of the presence or absence of connection of the communication device to the communication connection unit. If the communication device is connected, the communication system is switched to the communication system on the communication connection side, and if the communication device is not connected to the communication connection unit, the communication system is switched to the communication system on the communication driver side. In addition, the external circuit is a resistor connected between the communication data reception line and the power supply line from the communication device via the communication connection unit, and the internal circuit is connected between the communication data transmission line and the ground line to the communication device. It is a resistor connected between them.
According to the present invention, when the communication device is connected, when the communication port is not transmitted, the output port is switched to the input port and the voltage value of the transmission line to the communication device is read. , The transmission line becomes “H” level. In a state where the communication device is disconnected, the transmission line to the communication device is at the “L” level. Therefore, if the level of the transmission line when communication data is not transmitted is checked, it is possible to know whether the communication device is connected or not from the check result. This check is repeated periodically. When a communication device is connected to the communication connection unit, the communication system is switched to the communication connection side, and no communication device is connected to the communication connection unit. Is switched to the communication system on the communication driver side. With such switching control, two systems of communication are realized by one communication device.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail based on embodiments.
[ Reference example ]
FIG. 1 is a circuit diagram showing a connection state between a communication apparatus and a communication device according to the present invention. In the figure, 11 is a communication device such as an industrial temperature controller according to the present invention, 11-1 is a communication connection unit (digital communication connection unit) in the communication device 11, and 11-2 is built in the communication device 11. A CPU (central processing unit), 12 is a communication device such as a controller for control, and 13 is a communication cable for connecting the communication device 11 and the communication device 12. Communication is performed between the communication device 11 and the communication device 12 by a digital transmission method.
[0014]
In the communication device 11, the communication connection section 11-1 is configured by stereo jacks J1 and J2. By inserting a pin (not shown) at the tip of the communication cable 13 into the stereo jacks J1 and J2, The communication device 11 and the communication device 12 are connected. The stereo jack J1 is connected to the output port P1 of the CPU 11-2, and the stereo jack J2 is connected to the input port P2 of the CPU 11-2.
[0015]
A resistor R1 is connected as an internal circuit between the line connecting the stereo jack J1 and the output port P1 (transmission line for transmitting communication data to the communication device 12) L1 and the ground line. A resistor R2 is connected between a line (a reception line for communication data from the communication device 12) L2 connecting the stereo jack J2 and the input port P2 and a power supply line (Vcc line). On the communication device 12 side, a resistor R3 is connected as an external circuit between a reception line L3 for communication data from the communication device 11 and a power supply line (Vcc line).
[0016]
Transmission line when communication data is not transmitted from the CPU 11-2 in a state where the pin at the tip of the communication cable 13 is inserted into the stereo jacks J1 and J2 (a state where the communication device 11 and the communication device 12 are connected). The voltage value VP1 of L1, that is, the voltage value VP1 of the communication data output port P1 of the CPU 11-2 is a predetermined value different from the signal level of the communication data, VP1on = R1 / (R1 + R3) · Vcc. Transmission when the communication cable 13 is not transmitted from the CPU 11-2 in a state where the pin at the tip of the communication cable 13 is not inserted into the stereo jacks J1 and J2 (the communication device 11 and the communication device 12 are not connected). The voltage value VP1 of the line L1, that is, the voltage value VP1 of the output port P1 of the transmission data of the CPU 11-2 is VP1off = 0V.
[0017]
FIG. 2 is a flowchart showing processing operations unique to the present embodiment performed by the CPU 11-2 in the communication apparatus 11. The CPU 11-2 periodically repeats this processing operation. First, the CPU 11-2 checks whether or not communication data is being transmitted from the output port P1 to the communication device 12 (step 201). If communication data is not being transmitted (NO in step 201), it is determined that communication data has not been transmitted (waiting for reception other than transmission or being received), and the output port P1 is switched to an input port (step 202). The voltage value VP1 of the input port P1 is read (step 203).
[0018]
When the read voltage value VP1 is VP1on (= R1 / (R1 + R3) · Vc), the values of R1 and R3 are determined so that the comparison result is recognized as the “H” level. Thereby, when VP1 is VP1on (= R1 / (R1 + R3) · Vc), the comparison result is “H” level, and when V1off (= 0), the comparison result is “L” level. .
[0019]
When VP1 is VP1on, that is, when VP1 is at “H” level, the CPU 11-2 determines that the communication device 12 is connected, and sets the operation of the communication device 11 to the communication state (step S1). 205). When VP1 is VP1off, that is, when VP1 is at the “L” level, it is determined that the communication device 12 is not connected, and the operation of the communication device 11 is set to a non-communication state (step 206). After performing this operation setting, the port P1 is switched to the original output port (step 207).
[0020]
According to this reference example , there is no need to send a communication command from the communication device 12 to the communication device 11 in order to notify whether or not the communication device 12 is connected, and the communication device 11 can simply connect the communication device 12. The presence or absence can be detected. When the communication cable 13 is disconnected from the communication connection unit 11-1 after the communication state is set, the voltage value VP1 of the port P1 of the CPU 11-2 is VP1off (= 0V: “L” level). Therefore, it is automatically set to a non-communication state by a periodic check when communication data is not transmitted. In addition, since no communication command is sent, it is less susceptible to electromagnetic noise.
[0021]
Further, according to this reference example , in the case of poor contact of the communication connection unit 11-1 where communication is actually impossible, the voltage value VP1 of the port P1 of the CPU 11-2 is VP1off (= 0V: “L”. Therefore, it is automatically set to the non-communication state by a periodic check when communication data is not transmitted, and it is prevented that the communication state remains set even though communication is not possible. It is.
[0022]
Further, according to this reference example , in the case of poor contact of the communication connection unit 11-1 where communication is actually impossible, the communication cable 13 is connected to the stereo jacks J1, J2 of the communication connection unit 11-1 . It is possible to brush up by inserting / removing the pin at the tip several times to eliminate contact failure and return to a communicable state. In addition, since the output port P1 of the CPU 11-2 is also used as an input port when detecting whether or not the communication device 12 is connected, a new input port is not required.
[0023]
As described above, according to this reference example , in the communication device 11 that performs communication by the digital transmission method, the connection state with the communication device 12 that cannot be realized by the conventional connection determination circuit 71 (FIG. 5). Can be easily and reliably detected.
[0024]
Embodiment
FIG. 3 shows an embodiment of the present invention. In this embodiment , the communication device 11 is provided with a communication driver 11-3 so that two systems of communication can be performed. In this case, the CPU 11-2 controls the enable terminal 11-31 of the communication driver 11-3 using the serial communication interface (SCI), that is, the output port P3, as follows. Switch between the two systems.
[0025]
The CPU 11-2 detects the presence / absence of connection of the communication device 12 in the same manner as described in the reference example described above . When the connection of the communication device 1 is detected, the enable terminal 11-31 of the communication driver 11-3 is set to inactive, and the communication system is switched to the communication system on the communication device 12 side (communication connection unit 11-1 side) . When disconnection of the communication device 12 is detected, the enable terminal 11-31 of the communication driver 11-3 is set to active, and the communication system is switched to the communication system on the communication driver 11-3 side. By such switching control, two systems of communication can be realized with one SCI, the mounting space can be reduced, and the cost can be reduced.
[0026]
【The invention's effect】
As is apparent from the above description, according to the present invention, when the output port when communication data is not transmitted is switched to the input port by a combination with the external circuit on the communication device side connected via the communication connection unit. An internal circuit is provided that sets the voltage value of the transmission line of communication data to the communication device at “H” level when the communication device is connected and “L” level when the communication device is not connected. By periodically checking the communication device, the presence or absence of connection of the communication device to the communication connection unit is detected, so that the connection state with other communication devices can be simplified in the communication device that performs communication by the digital transmission method. And it becomes possible to detect reliably.
In addition, when a communication device is connected to the communication connection unit, the communication system is switched to the communication connection side, and when no communication device is connected to the communication connection unit, the communication driver side is switched. By switching to a communication system, such switching control can realize two systems of communication with a single communication device, reducing the mounting space and reducing the cost.
[Brief description of the drawings]
FIG. 1 is a circuit diagram ( reference example ) showing a connection status between a communication apparatus and a communication device according to the present invention.
FIG. 2 is a flowchart showing a specific processing operation performed by a CPU built in the communication apparatus shown in FIG.
FIG. 3 is a circuit diagram ( embodiment ) showing a connection state between the communication apparatus and the communication device according to the present invention.
FIG. 4 is a diagram showing a connection state between a conventional industrial temperature controller and a controller for control.
FIG. 5 is a circuit diagram disclosed in Japanese Utility Model Laid-Open No. 63-129351.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Communication apparatus, 11-1 ... Communication connection part (digital communication connection part), 11-2 ... CPU (central processing unit), 11-3 ... Communication driver, 12 ... Communication apparatus, 13 ... Communication Cable, R1... Resistor (internal circuit), R3... Resistor (external circuit).

Claims (1)

In a communication device that is connected to another communication device via a communication connection unit and performs communication with the connected communication device by a digital transmission method,
The voltage value of the transmission line of the communication data to the communication device when the communication data non-transmission output port is switched to the input port by the combination with the external circuit on the communication device side connected via the communication connection unit An internal circuit which is set to “H” level when the communication device is connected and “L” level when not connected,
A communication driver provided in a communication system different from the communication system on the communication connection side;
A communication device connection detection means for detecting the presence or absence of connection of communication devices the voltage value of the transmission line when the communication data not yet sent to periodically check the communication connection unit,
Based on the detection result of the communication device connection detection means, when a communication device is connected to the communication connection unit, the communication device is switched to the communication system on the communication connection unit side, and the communication device is connected to the communication connection unit. If not, communication system switching means for switching to the communication system on the communication driver side,
The external circuit is a resistor connected between a reception line and a power line of communication data from a communication device via the communication connection unit,
The communication device according to claim 1, wherein the internal circuit is a resistor connected between a transmission line of communication data to the communication device and a ground line .

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