JPH0710071B2 - Information transmission device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an information transmission device in which a plurality of terminals are connected to an information transmission line composed of a signal line having a positive polarity and a signal line having a negative polarity. It is about.

[Prior Art] FIG. 3 is shown, for example, in "Research Report Group on Informatization at Home (Final Report) -Technical Standardization Edition" issued by the Research Group on Informatization at Home in March 1986. FIG. 1 is a circuit diagram showing a conventional information transmission device, in which (1) is an information transmission line (hereinafter referred to as a transmission line), and this transmission line (1) has a signal line ( 1a) and a signal line (1b) having a negative polarity. (2) and (7) are connected to each other via the transmission line (1),
A terminal device that transmits information by an AMI-encoded baseband signal, and the terminal devices (2) and (7) are respectively a coupling circuit (3) and a transmission circuit that couple the terminal device to the transmission path (1). It has (4), a receiving circuit (5), and a transmission control circuit (6).

Hereinafter, the configuration of each unit will be described in detail. The coupling circuit (3) has terminals (31) and (32) as input terminals and this terminal (3
Capacitor (3
a) and (3b) and a coupling transformer (3c) having windings (3d), (3e) and (3f).

The transmitter circuit (4) is the winding (3e) of the coupling transformer (3c),
Transistors (4a) and (4c) with the collector connected to (3f) and the emitter connected to ground, and the base resistor (4
b) and (4d), and the other ends of the resistors (4b) and (4d) are connected to the transmission control circuit (6). These transistors (4a) and (4c) are turned on every time the code "0" is transmitted.
N, OFF and send AMI code.

The receiving circuit (5) has one of the input terminals coupled to the transformer (3c).
Of the comparators (5a) and (5b), which are connected to the windings (3e) and (3f), and the other input terminal is connected to the reference voltage generating terminal consisting of a series circuit of resistors (5e) and (5d). It is composed of an OR circuit (5c) using the output terminals of the comparators (5a) and (5b) as input terminals, and the output terminal of this OR circuit is connected to the transmission control circuit (6).

In the AMI code transmitted to the transmission line (1), a signal transmitted to the positive polarity is generated in the winding (3e), the level is determined by the comparator (5b), and the AMI code is converted into the NRZ signal. When the transmission signal has a negative polarity, the level is judged by the comparator (5a) via the winding (3f) and converted into an NRZ signal. Therefore, this receiving circuit (5) is a circuit for converting an AMI code into an NRZ signal.

The transmission control circuit (6) is composed of a microcomputer or the like, and when transmitting the AMI code to the transmission line (1), first the transmission terminal (6b) is held for 1 bit to transmit the code "0" as a start bit. When controlling the high level and then transmitting the code “0”, the transmitting terminal (6a) is controlled to the high level, and when transmitting the signal “1”, both terminals (6a) and (6b) are set to the low level. Control. Therefore, the transmission control circuit (6)
Is a transmission terminal (6b) for transmitting a signal with positive polarity,
It has a transmission terminal (6a) for transmitting a signal with a negative polarity and a reception terminal (6c) connected to the output of the reception circuit (5) for receiving the signal transmitted to the transmission line (1). .

The information transmitting apparatus having the above-mentioned structure assembles and disassembles the transmission packet as shown in FIG. 4 and, as shown in FIG.
When the collision is detected by comparing the transmission data transmitted from the transmission terminals (6a) and (6b) with the data transmitted to the transmission path (1), the transmission is stopped when the collision occurs and it can be considered that the other device lost. To do.

Next, the operation will be described. When a transmission request is made, the transmission control circuit (6) confirms from the signal at the reception terminal (6c) that the transmission line (1) is in the idle state, and then the packet configuration as shown in FIG. 4 (a). And the character is transmitted by the AMI code from the start bit (SB) for character synchronization as shown in FIG. 4 (b). In FIG. 4, PR is a priority code, SA is a self address, DA is a partner address, CW is a control code, BC is a message length, DATA is data, and FC.
C indicates a check code.

This start bit (SB) is transmitted so that the signal line (1a) has a positive polarity. This is for start-stop synchronization between terminals and for detecting collision of data transmitted by a large number of terminals (2) and (7) connected to the transmission path (1).
That is, as shown in FIG. 5, the data transmitted by the terminal (2) (FIG. 5 (a)), the data transmitted by the terminal (7) (FIG. 5 (b)), and the result thereof. The data collision on the transmission line (1) is detected from the difference between the data (FIG. 5 (c)) transmitted on the transmission line (1).

That is, when the transmission terminal (6b) of the transmission control circuit (6) is set to high level for a period of 1 bit corresponding to the start bit, the transistor (4c) is turned on and the power supply voltage is applied to the winding (3f). This power supply voltage is induced in the winding (3d),
The illustrated polarity, that is, the signal line (1a) is applied to the transmission line (1) via the capacitors (3a) and (3b) so as to have a positive polarity.

Next, when transmitting the code "0", the transmission control circuit (6)
Sets the transmission terminal (6a) to high level, and the transistor (4
By turning on a), a reverse voltage is generated in each winding of the coupling transformer (3c), and the signal is transmitted to the transmission line (1) in a polarity such that the signal line (1b) has a positive polarity.

When transmitting the code “1”, the transmission control circuit (6) sets both the transmission terminals (6a) and (6b) to the low level. At this time, turn on / off the transistors (4a) and (4c)
The code "0" and the code "1" transmitted by the FF are always level-determined by the comparators (5a) and (5b), converted into the NRZ signal by the OR circuit (5c), and transmitted by the transmission control circuit (6). Collision detection is performed as shown in FIG. 5 by comparing the data with the received data transmitted from the receiving circuit (5) to the transmission path (1).

That is, when the terminals (2) and (7) simultaneously transmit signals, first, the start bit code “0” is simultaneously transmitted with the same authenticity, so that the transmission path (1) is shown in FIG. The code "0" is transmitted as in c).

Since the next code "1" is also the same signal in the two terminals (2) and (7), the code "1" is transmitted through the transmission path (1). Further, when the terminal device (2) transmits the code “0” and the terminal device (7) transmits the code “1”, the code “0” is transmitted to the transmission path (1).
Is transmitted, and the terminal device (7) transmits the transmission data and the transmission path (1).
Collision is detected from the difference in the received data received from, and only reception is performed thereafter.

[Problems to be Solved by the Invention] Since the conventional information transmission device is configured as described above, the signal applied to the transmission line has a polarity in order to reliably detect the collision of the signal. It was necessary to identify the polarity when connecting the device to the transmission line, and there was a problem that mistakes occurred due to wiring work.

The present invention has been made to solve the above problems, and an object of the present invention is to obtain an information transmission device capable of making a connection terminal of a terminal device nonpolar when connecting the terminal device to a transmission line.

[Means for Solving Problems] An information transmission apparatus according to the present invention connects a plurality of terminals for serially transmitting an encoded baseband signal with a predetermined polarity using start / stop synchronization to an information transmission line. , A polarity detection circuit for detecting the polarity of the start bit first received after the power is turned on, and a switching circuit for switching the polarity of the encoded baseband signal according to the output of the polarity detection circuit for each of the terminals. It is equipped.

[Operation] In the information transmission device of the present invention, when the polarity of the start bit is detected and the switching circuit switches so that the polarities of the start bits of the transmission data are the same, when the terminal device is connected to the transmission line, The input terminal can be made non-polar, which prevents mistakes in wiring work.

[Embodiment of the Invention] An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1 in which the same parts as those in FIG. 3 are denoted by the same reference numerals, (5) is a receiving circuit, and the output terminals of the comparators (5a) and (5b) which are the constituent elements of this receiving circuit (5) are It is connected to the polarity determination terminals (6d) and (6e) of the transmission control circuit (6). That is, when the signal line (1a) of the transmission line (1) has the positive polarity, the terminal (6d) becomes high level, and when the signal line (1a) has the opposite polarity, the terminal (6e) becomes high level.

(8) is a polarity switching circuit. This polarity switching circuit (8)
Is a resistor (13) at the switching terminal (6f) of the transmission control circuit (6).
A transistor (12) whose base is connected through the emitter and whose emitter is connected to the ground, and a relay (9) which is connected to the collector of this transistor (12) and has bipolar contacts (10) (11). It is configured.

The normally open contact (10a) of the contact (10) and the normally closed contact (11b) of the contact (11) are connected, and these are connected to the transmission terminal (6
connected to a). Also, the normally closed contact (10
b) and the contact (11) normally open contact (11a) are connected,
These are connected to the transmission terminal (6b).

On the other hand, the common contacts (10c), (11c) of the contacts (10), (11)
Are the transistors (4a) and (4
It is connected via the base resistors (4b) and (4d) of c). The switching terminal (6f) is a high bit and vice versa when the polarity judgment terminal (6e) becomes high level before the judgment terminal (6d) by the start bit received after packet reception becomes possible. If the terminal (6d) goes high first, it outputs low level.

Reference numeral (6) is a transmission control circuit, which is composed of a microcomputer or the like, and the polarity determination and output to the switching terminal (6f), the transmission terminals (6a) and (6b) are realized by software.

The transmission terminal (6b) is a start bit transmission terminal, and is at a high level for a period of 1 bit for transmitting the start bit that is the code "0", and when transmitting the code "0" next time, the transmission terminal (6a) Is set to the high level, and thereafter, every time the code “0” is transmitted, the transmission terminals (6a) and (6b) are alternately set to the high level and the AMI code is transmitted to the transmission line (1).

FIG. 2 is a flowchart showing the operation, and the operation will be described below with reference to this flowchart. When the input terminal (31) of the terminal device (2) is connected to the signal line (1a) and a power supply (not shown) is applied, the transmission control circuit (6) enters a reception standby state.

At this time, a signal is transmitted from the other terminal device (7) to the transmission line (1) with the packet structure and the character structure shown in FIG. That is, the code "0" that is the start bit (SB)
The signal transmitted from the terminal device (7) so that the signal line (1a) has a positive polarity by the capacitor (3a), (3
It is applied to the winding (3d) of the terminal (2) via b).

The voltage induced in the winding (3e) by the signal having such a start bit (SB) is compared with the reference voltage of the resistors (5e) and (5d) by the comparator (5b) to determine the level. If the received voltage is higher, it is considered that the code “0” has been transmitted, and a high level is output to the polarity determination terminal (6d) to determine the transmission polarity of the code “0”. At the same time, the high level output of the comparator (5b) is applied to the reception terminal (6c) as reception data via the OR circuit (5c).

The transmission control circuit (6) constantly monitors the polarity determination terminals (6d) and (6c) in the reception standby state. When the code "0" of the reception data is applied to the reception terminal (6c), the transmission control circuit (6) starts the reception process and looks at the internal transmission polarity determination flag (step ST-21).

When this flag is "0", that is, when the transmission polarity is not determined, it is determined which of the polarity determination terminals (6d) and (6e) the start bit (SB) is applied to (step ST-22).

Here, since the terminal (6d) is at a high level, the transmission control circuit (6) considers that the signal line (1a) has a positive polarity, and sets the control terminal (6f) to a high level (step
ST-23), transistor (12) is turned on, and relay (9) operates. As a result, the normally open contacts (10a), (11a) are connected to the common contacts (10c), (11c), the transmission terminal (6a) is the base of the transistor (4a), and the transmission terminal (6b) is the transistor (4c). Respectively connected to.

After that, the transmission polarity determination flag is set (step ST-2
5) and receive data from the receiving terminal (6c) (step S
T-26). After that, when a transmission request is issued to the transmission control circuit (6), the idle of the transmission path (1) is confirmed in the same manner as in the conventional device, and then the code "PR" (priority code) start bit is displayed as shown in FIG. 0 "is transmitted. That is, by setting the start bit transmission terminal (6b) to a high level for one bit and turning on the transistor (4c), the signal line (1a) of the transmission line (1) has a polarity such that the start bit has a positive polarity. Every time a code “0” is transmitted according to the AMI code, the transmission terminals (6a) and (6b) are alternately set to the high level to transmit the signal with the AMI code.

Further, the input terminals (31) and (32) of the terminal device (2) have polarities opposite to those shown in the figure, that is, the input terminal (31) has a signal line (1b),
Assuming that the input terminal (32) is connected to the signal line (1a) and the power is turned on, when a signal is transmitted from the terminal device (7) in the same manner as in the above embodiment, the start bit (SB)
The signal line (1b) has a positive polarity. Because of this, winding (3d)
The capacitor (3b) is applied to the positive polarity,
The voltage induced in the winding (3f) is level-determined by the comparator (5a), and the polarity determination terminal (6e) is set to high level.

As a result, the terminal (6e) is at the high level in the polarity judgment of the start bit (SB) (step
ST-22), control terminal (6f) is set to low level (step ST-24), transistor (12), relay (9)
Turn off. That is, the start bit transmission terminal (6b) is connected to the transistor (4b) via the normally closed contact (10b) and the resistor (4b).
It is connected to the base of a).

When a transmission request is sent to the transmission control circuit (6) in this state, the start bit transmission terminal (6b) goes high, the transistor (4a) turns on, and the winding (3d) of the coupling transformer (3c) has a capacitor. The code "0" of the start bit is transmitted in the polarity in which the side (3b) has a positive polarity. As a result, since the input terminal (32) is connected to the signal line (1a), the start bit can be transmitted so that the signal line (1a) has a positive polarity.

In the above embodiment, the switching of the transmission polarity of the start bit is performed by the relay contact which is the switch element inserted between the transmission terminals (6a) and (6b) and the transmission circuit (4).
This switch element is connected to the transmission circuit (4) and the coupling circuit (3),
Alternatively, it may be inserted between the input terminals (31) and (32) and the transmission path (1).

In addition, the polarity can be switched by changing the start bit (S
Instead of the control terminal (6f) H set (step ST-23) in the post-processing of polarity determination (step ST-22) in B), the start terminal transmission terminal is set to the transmission terminal (6b) and the control terminal (6b) is set. 6f) Instead of L set (step ST-24), set the start bit transmission terminal to the transmission terminal (6a).
The polarity switching may be performed by the shift wear of the transmission control circuit (6).

If all terminals are powered on at the same time, there will be no terminals that can transmit.Therefore, a specific terminal sends a signal for polarity determination that indicates a start bit at a predetermined cycle after powering on.
You may comprise so that it may transmit on a transmission line (1).

The polarity determination signal is, for example, one character of the packet shown in FIG. 4 (a), or the start bit (SB) and the 0th bit (b ₀ ) of the characters shown in FIG. 4 (b).
Should be set to the code “0” and transmitted. Further, the cycle may be set longer than the maximum length of the packet. In the above description, the case where the baseband signal is AMI-encoded and transmitted, but another encoding method such as NRZ is used.
But it is okay.

[Effects of the Invention] As described above, according to the present invention, the polarity of the start bit received first after the power is turned on is detected, and the transmission polarity is switched according to the detected output. When connecting to, there is an effect that the input terminal can be made non-polar, and troubles due to mistakes in wiring work can be prevented.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an information transmission device according to an embodiment of the present invention, FIG. 2 is a flow chart diagram showing its operation, FIG. 3 is a circuit diagram showing a conventional information transmission device, FIG. 4 and FIG. The figure is a diagram showing signals transmitted to a transmission line for explaining the operation. In the figure, (1) is an information transmission path, (2) and (7) are terminals, (6) is a transmission control circuit, (6d) and (6e) are polarity determination terminals, and (8) is a switching circuit. . In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (2)

[Claims] 1. An information transmission line composed of a signal line having a positive polarity and a signal line having a negative polarity when transmitting a signal, and a start bit having a predetermined polarity, each of which is connected to the information transmission line. Baseband signals encoded in the AMI system are serially transmitted with a predetermined polarity, start-bit synchronized with each other, and information transmission is performed by comparing the signal polarity on the information transmission line with the polarity of the signal sent by itself. In an information transmission device having a plurality of terminals for detecting signal collision on the road, each of the terminals has a polarity detection circuit for detecting the polarity of a start bit first received after power-on,
According to the output of the polarity detection circuit, a switching circuit is provided for switching the polarity of the AMI-encoded baseband signal transmitted to the information transmission path to the same polarity as the polarity detected by the polarity detection circuit. An information transmission device characterized by: 2. A specific terminal device among a plurality of terminal devices sends out a start bit determination signal including a start bit to a transmission path at a predetermined cycle, according to claim (1). Information transmission device described.