JPH02104147A - Communication device - Google Patents

Abstract

PURPOSE:To aquire a transmission line with a simple constitution as if communication of 1 to 1 is executed by confirming that no DC voltage is impressed to a control line prior to the start of communication in the transmission line consisting of the control line and a signal line and then impressing a DC voltage to the control line. CONSTITUTION:The transmission line is formed by the control line 101 and the signal line 102. In the case of transmitting data from a POS register 104 to a host computer 110, a control line of RS-232C is set up. When the voltage of a terminal 1 exceeds a fixed voltage, a voltage detecting circuit 3 outputs a signal to a logical part 7. When no output is generated from the circuit 3 at the time of setting the control line of RS-232C, a communication equipment 103 controls a power supply circuit 8 by the operation of the logical part 7 and impresses a positive voltage to the terminal 1 to aquire the control line 101. Thus, the control line 101 is aquired by the operation of control line of an RS-232C interface and then the POS register and the host computer can execute communication as if communication of 1 to 1 is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a communication device for connecting a plurality of devices by wire and allowing them to communicate with each other.

2. Description of the Related Art In recent years, local area network (hereinafter referred to as LAN) data communication has become popular. For example, products called Ethernet LAN, Star LAN, and Token Ring LAN have been commercialized. In any of these LAN systems, when two devices communicate with each other, data transmission for connection is performed between each device before communication.

Problems to be Solved by the Invention Conventional LANs require complicated communication procedures to communicate between two terminal devices, and therefore, a large-scale communication device to carry out the communication procedures is connected to the terminal device and the transmission path. It was necessary during

Another problem is that the communication devices are generally expensive.

In view of the above problems, the present invention provides a communication device that does not require a complicated communication procedure to communicate between two terminal devices and can be configured at low cost.

Means for Solving the Problems In order to solve the above problems, the communication device of the present invention includes a transmission line having a control line and a signal line, and a control line monitoring circuit that monitors the presence or absence of a signal on the control line m1. , and a power supply circuit that applies a DC voltage to the control line.

Operation According to the above-described configuration, the present invention acquires the right to use the signal line by applying a DC voltage to the control line after confirming that no DC voltage is applied to the control line before starting communication. Instead, two terminal devices that wish to communicate can be regarded as if they were connected one-to-one, and no special communication procedure is required. Therefore, the communication device can be constructed at low cost.

Embodiment Hereinafter, a communication device which is an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a communication device in a first embodiment of the present invention. In Figure 1, 1 is the connection point with the control line, 2 is the connection point with the signal line,
3 is a control line voltage detection circuit, 4 is a control line collision detection circuit, 6
is a control line positive/negative detection circuit, 6 is a control line monitoring circuit, 7 is a logic section, 8I-i power supply circuit, 9 is a signal line carrier detection circuit,
10 is a signal line collision detection circuit; 11 is a signal line transmission/reception circuit;
12 is a logic section, 13 is an interface section, and 14 is a switch provided in the logic section 7. Turning this switch 14 on or off controls data transmission and reception of this communication device. The switch 14 is set to be on or off depending on the type of terminal to be connected.

Regarding the communication device configured as described above, the first
The operation will be explained using FIG. FIG. 2 shows an example of application using the communication device of the present invention shown in FIG. In FIG. 2, 101 is a control line, 102 is a signal line, and the 101 table 102 forms a transmission path. 1
03,105°107, 109 are the communication devices shown in FIG. 104°106.108. ．． 110 is a terminal device, 104, 106 and 108 are PoS registers located on each floor, and 110 is a host computer located in the management room. The embodiment shown in FIG. 2 is an example where the system is installed in a restaurant or a department store.

Communication is between the PoS register and the host computer, and basically there is no communication between POS registers.

First, the POS register 104 is connected to the host computer 110.
We will explain the case of sending data to . Communication device 1
03 and the POS register 104 are connected by R3-232C.

When the PoS register 104 has data to be sent,
Set up a control 8-wire DTR of 6'-232C. The voltage detection circuit 3 outputs a signal to the logic section 7 when the terminal 1 exceeds a predetermined voltage, whether it is a positive voltage or a negative voltage. When the control line DTR of R8-2320 is disconnected, communication device 1
03 controls the stain source circuit 8 by the action of the logic section 7 to apply a positive voltage to the terminal 1 and obtain the control line 101 when there is no output from the voltage detection circuit 3. Therefore, a positive voltage is applied to the control line 101. When control line 101 is acquired, R8
-232C terminal DSR is set up and PoS register 104
informs that the control line has been acquired. If control line DT
If there is an output from the voltage detection circuit 3 when R is reached, it is assumed that one of the other communication devices 10E5, 107゜109 has acquired the control line, and the positive voltage from the power supply circuit 8 is applied to the terminal 1. Do not apply any voltage. Also R3-232
Do not set up the 0 terminal DSR. POS register 104 has terminal DSR even though terminal DTR is set up.
We know that we have failed in acquiring the υ control line because the movement does not occur. When the collision detection circuit 4 detects that an abnormal current flows through the terminal 1, it outputs a signal / and H to the logic section 7. Suppose that the communication device 103 outputs a positive voltage to the control M101 and at the same time the communication device 109 outputs a negative voltage to the control tA101. Then, the positive voltage and the negative voltage collide on the control line 101, causing an excessive current to flow to the terminal 1. The collision detection circuit 4 detects this excessive current and notifies the logic section 7 that a collision has occurred. If there is a collision, the logic section 7 controls the power supply circuit 8 to stop applying voltage to the terminal 1.

Then, the terminal DSR of R5-232C is lowered via the interface 13. This allows it to be known that there has been a collision on the υPoSPOS register 104 line. Now, if the control line is acquired, the POS register 104 sends the transmission data to the communication device 103. In the communication device 103, a carrier detection circuit 9 detects whether there is a signal at the terminal 2.
When there is no output, the logic section 12 works to output the transmission data from the 5pos register 104 as it is to the terminal 2 via the transmission/reception circuit 11. If a collision of signals should occur on the signal line 102, the collision detection circuit 10 detects the collision and notifies the logic section 12 of the collision. Logic unit 12 then immediately acts to stop the data transmission.

Next, consider the case of reception. The data transmitted on the signal line 102 is input to the communication device 1ob, 107°109. Among them, the communication device 106 and 107 are controlled by the positive/negative detection circuit 5? 8 wire 101 (terminal 1) i/1CJllE
Detects that voltage is applied. This communication device 1
The switch 14 connected to the logic unit 7 of the OS, 107 is set to be on in advance. Therefore, when the logic section 7 detects that a positive voltage is applied by the positive/negative detection circuit 6, it acts on the logic section 12 to prohibit the transmission and reception of data on the signal line. Therefore, the data input to terminal 2 is discarded by logic section 12, and no change occurs on R3-232C. Note that when the switch 14 is on, the logic section 7 controls the E power supply circuit so as to apply a positive iTf voltage to the terminal 1 when the control line is acquired. Furthermore, I am the control line 10
When 1 is not acquired, the line IS is configured such that data can be transmitted and received on the signal line 102 only when a negative voltage is applied to the control line 1o1.

On the other hand, the communication device 109 also detects that a positive voltage is applied to the control line 101 (terminal 1) by the positive/negative detection circuit 6. The switch 14 connected to the logic section 7 of this communication device j09 is set to OFF in advance. switch 1
4 is off, data transmission/reception on the signal line 102 is possible even when the control line 101 is not acquired. Therefore PoS register 10
4 is received by the transmitter/receiver circuit 11, and the data from the logic section 1
2. Transmitted to host computer 110 by R3-2320 via interface 13; Note that when the switch 14 is off, the logic section 7 controls the power supply circuit 8 so as to apply a negative voltage to the terminal 1 when the control line is acquired for one period.

As described above, according to this embodiment, the control line 101 is acquired by operating the control line of the RS-2320 interface, and thereafter, communication between the POS register and the host computer is performed as if it were one-to-one communication. Can be done. Furthermore, due to the action of the switch 14, when working as a communication device for the PoS register, unnecessary data received from other POS registers etc. is discarded by the communication device so that it is not transmitted to the PoS register. communication load can be reduced.

Effects of the Invention As described above, the present invention obtains a transmission path with a simple configuration, and
After that, it is possible to provide a communication device that can be regarded as one-to-one communication even if it is not done, so there is an advantage that no special communication procedures are required for terminal devices such as POS registers and host computers. Moreover, since the communication device of the present invention itself has a simple configuration, it can be manufactured at low cost.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a communication device according to an embodiment of the present invention, and FIG. 2 is a diagram showing an embodiment using the communication device of the present invention. 1... Connection point with the control line, 2... Connection point with the signal line, 3... Control line voltage detection circuit, 4...
Control line collision detection circuit, 6...Control line positive/negative detection circuit, 6...Control line monitoring circuit, 7...Logic section, 8
...Power supply circuit, 9...Signal line carrier detection circuit, 1o...Signal line collision detection circuit, 1;...
...Signal line transmitting and receiving circuit, 12...Logic section, 13
...Interface section, 14...Switch, 101...Control line, 1o2...Signal line, 103, 105, 10 end, 109...
・Communication device, 104.106, j os=-=-po
s'v register, 110...Host computer.

Claims (2)

[Claims] (1) A transmission line having a control line and a signal line, a control line monitoring circuit that monitors the presence or absence of a signal on the control line, and a power supply circuit that applies a DC voltage to the control line. Communication device. (2) The communication device according to claim 1, comprising a power supply circuit having a switching function of applying a positive voltage or a negative voltage to the control line.