JPH03113938A - Line connection circuit - Google Patents

Abstract

PURPOSE:To save power consumption by supplying power to a line forming means of one equipment only when other equipment being its communication opposite party is in operation. CONSTITUTION:A notice circuit 18 detects whether an operating power supply of a terminal equipment 2 is in the drive level or not, informs it to a maser set 1 that the terminal equipment 2 is in the operating state when the power supply is in the drive level and the master set 1 turns on/off a transistor(TR) 24 of a switch circuit 23 by the operating state notice signal and supplies power to buffers 4a, 4b, 7, 10 and resistors 5, 6, 8, 9 being the line forming means only when the TR 24 is turned on to establish the communication line. Since the power supply to the said line forming means in the master set 1 is established only when the terminal equipment 2 being its communication opposite party is in the operating state, power consumption at undesired time is prevented.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention provides a system for performing data communication between units such as a converter device, and a method for connecting two devices to enable the data communication. The present invention relates to a line connection circuit that connects together to provide a signal transmission path.

(Prior Art) Conventionally, in communication related to information processing, a system as shown in FIG. 2 is usually used.

In FIG. 2, numeral 1 denotes a main unit consisting of a microcomputer, which is also called a main station, and numeral 2 denotes a terminal consisting of its expansion unit, printer, etc. The main device 1 and the terminal 2 are connected by a cable 3 with a connector. This cable 3 includes a data transmission line and an expansion board 2a.
+ 2 b + ... is memory or human output (I 1
0), control signal lines, address designation lines, etc. that instruct reading/writing to these are included.

In each device 1, 2, before the connectors 3a, 3b,
Each of them is provided with a bus sofa serving as a driver or a receiver, and a terminating resistor that performs impedance matching to prevent signal reflection. Communication between the apparatuses 1 and 2 is performed with the power switches is and 2s turned on, respectively, and a communication line established by supplying [[ to their buffers and terminating resistors.

However, conventionally, in this type of system, as long as the main device 1 is powered on, power is supplied to the buffer and the terminating resistor, and power is consumed, which has been a problem from the viewpoint of energy saving.

In other words, terminal 2 is not connected, or
When terminal 2 is not in operation, the buffer and terminating resistor described above are not required, but even in such a case, if it is powered on, power will be supplied, which will save wasted power. This means that you are consuming it.

In addition, there is a conventional method that deals with this type of power consumption problem, as shown in Japanese Patent Application Laid-Open No. 64-70819, but this method does not depend on whether a terminal is connected to the main device or not. The power supply is controlled only by the system, and it is still far from being sufficient.

(Problem to be Solved by the Invention) As described above, this type of communication system has the problem that as long as the main device 1 is powered on, power is consumed even though it is not necessary.

The present invention was made in view of these problems.
The purpose is to provide a line connection circuit that can save power in a communication system.

[Structure of the invention]

(Means for Solving the Problems) A line connection circuit of the present invention is configured to control power supply to line forming means provided in one of two devices that communicate with each other. detects whether the operating power supply of the other device is at the drive level, and when it is at the drive level, notifies the one device that the other device is in the operating state, and In this system, the switch means is turned on and off by this operating state notification signal, and only when the switch means is in the on state, power is supplied to the line forming means to establish a communication line.

(Function) According to the line connection circuit of the present invention, power is supplied to the line forming means in one device only when the other device, which is the communication partner, is in an operating state.
It is possible to prevent unnecessary power consumption.

(Example) Examples of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram of a line connection circuit according to an embodiment of the present invention. In the embodiment shown in this figure, power is supplied to the buffer and terminating resistor of the main device 1 only when the terminal device 2 is powered on.

That is, first, the cable 3 includes parallel bidirectional signal transmission lines 3c, 3c, . . . and unidirectional signal transmission lines 3d, 3e. Transmission line 3c, 3c
+... are used as data transmission lines, and for example, eight lines are provided in the case of 8-bit parallel. The one-way transmission lines 3d and 3e are used as control signal lines for read/write and the like.

The cable 3 is further provided with operating state notification lines 3f and 3g for notifying the main device that the terminal device 2 is powered on and in an operating state.

Note that the signal transmission line serving as the address line is not shown here because it is almost the same as the data transmission line.

The main device 1 is provided with a driver/receiver IC4, and this IC4 connects a parallel circuit consisting of a driver buffer 4a and a receiver buffer 4b to a signal transmission line 3C.
Contains the number of books. Each parallel circuit is connected to each signal transmission line 3C, and controls the connection and directionality of the data transmission line. This IC4 has a power supply voltage V
eal is applied through the power supply line 27, and each buffer 4a, 4b of the IC4 operates while this power supply voltage Vcc1 is applied.

One end of each of antireflection terminating resistors 5 and 6 is connected to each connection point between each parallel circuit of the IC 4 and each signal transmission line. The other end of the resistor 5 is connected to the power supply line 27, and the other end of the resistor 6 is grounded.

The main device 1 further includes a driver buffer 7 consisting of an IC.
and a receiver buffer 10 are provided. The driver buffer 7 is connected to the signal transmission line 3d, the receiver buffer 10 is connected to the signal transmission line 3e, and both 7 and 10 are used to control on/off of the control signal transmission line.

A power supply voltage Veal is applied to these buffers 3d and 3e through a power supply line 27, and this power supply voltage Veal
Operates while receiving el.

The respective negative ends of anti-reflection terminating resistors 8 and 9 are connected to the connection point between the driver buffer 7 and the signal transmission line 3d. The other end of the resistor 8 is connected to the power supply input 27,
The other end of resistor 9 is grounded.

The terminal device 2 is provided with a driver/receiver IC 11, and a parallel circuit consisting of a driver buffer 11a and a receiver buffer 11b is connected to a signal transmission line 3C.
Contains the number of books.

Each of these parallel circuits is connected to each signal transmission line 3C,
It is supposed to control the connection and direction of the data transmission path. A power supply voltage Vcc2 is applied to this ICII, and each buffer ylla, llb of IC11 is
It operates while this power supply voltage V ec2 is applied.

One end of an anti-reflection terminating resistor 12, 13 is connected to each connection point between each ICII parallel circuit and each signal transmission line. A power supply voltage Vcc2 is applied to the other end of the resistor 12, and the other end of the resistor 13 is grounded.

The terminal device 2 is further provided with a driver buffer 14 and a receiver buffer 15, each of which is an IC. The driver buffer 14 is connected to the signal transmission line 3d, the receiver buffer 15 is connected to the signal transmission line 3e, and both 14 and 15 are used to control on/off of the control signal transmission line. A power supply voltage V cc2 is applied to these buffers 14 and 15, and this power supply voltage V cc2
It operates while receiving.

Here, regarding the configuration so far, for example, the terminal device 2
Consider a case where the user wants to obtain predetermined data from the main device 1.

In this case, the terminal device 2 is connected to the main device 1 by a cable 3, and the switch IS of both devices 1 and 2 is connected.

2S is turned on to enable the above communication.

In this state, the terminal device 2 issues a transmission request through the driver buffer 14.

The main device 1 receives the transmission request through the line 3d and the receiver buffer 7, and in response notifies the driver through the driver buffer 10 that the data will be output.

The terminal device 2 receives the notification through the line 3e and the receiver buffer 15, and in response, the terminal device 2
The buffer lla of each bit of is turned on, and the reception ready state is transmitted through the same route as the transmission request.

In response to this, the main device 1 turns on the driver buffer 4a of each bit in the IC4. And buffers 4a, 4a, . . . , line 3c.

3c, . . . This data is stored in the receiver buffer 11 a on the terminal device 2 side.
11a, . . .

In contrast to this data transmission direction, when the terminal device 2 is on the data transmitting side and the main device 1 is on the data receiving side, the driver buffer 11 of the IC 11 on the terminal device 2 side is
b is turned on, and on the main device 1 side, the receiver buffer 4b of the IC 4 is turned on.

As mentioned above, here, the buffers 4a and 4b.

7.10 and terminating resistor5. 6. 8. 9 constitutes a line forming means.

Now, 18 is an operating state notification circuit that constitutes a part of the operating state notification means. This operating state notification circuit 18 is provided in the terminal device 2 and includes a constant voltage diode 19, an NPN type transistor 21, a base resistor 20, and a bias resistor 22.
It is equipped with A power supply voltage Vcc2 is applied to the anode of the constant voltage diode 19. When the switch 2s is off, the power supply voltage Vcc2 is not generated, so the diode 19 is in a non-conducting state,
The transistor 21 is turned off and its collector becomes H.
”.When the switch 2s is turned on, when the voltage level of the power supply line 28 approaches Vcc2, the diode 1
9 becomes conductive, transistor 21 is turned on, and the collector becomes "L".

The collector of this transistor 2 is connected to a signal transmission line 3f, and the emitter thereof is connected to a line 3g.

Reference numeral 23 denotes a switch circuit for power supply control. This switch circuit 23 is provided in the main device 1 and consists of a PNPN upper type resistor 24, its base resistor 25, and a bias resistor 26. The base of the transistor 24 is connected to the transmission line 3f via the base resistor 25, and is turned on when the transmission line 3f is aL'. A power supply voltage V eel is applied to the emitter of this transistor 24, and its collector is connected to the power supply line 27. The buffers y4a, 4b, 7.10 and the resistor 5°6.8.9 Only when 24 is on, the power supply voltage V
eel is applied.

Therefore, first, assuming that the terminal device 2 is not connected to the main device 1, the line 3f becomes "H" and the transistor 24 is turned off, so no current flows through the power supply line 27 and the buffers 4a and 4b .

7.10 and resistors 5, 6, 8.9, power supply voltage VccL
is not supplied.

Furthermore, even if the terminal device 2 is connected, if its power switch 2s is turned off, the constant voltage diode 1
9 is not applied with the power supply voltage Vcc2 and becomes non-conductive.

Therefore, transistor 21 is off and line 3f is “
H", the transistor 24 is turned off, and the buffers 4a, 4b,
7°10 and resistance 5. 6.8.9, power supply voltage Vce
1 is not supplied.

Next, when the switch 2s of the terminal device 2 is turned on,
Buffers lla and llb of the same device 2.

14.15 and the terminating resistor 12.13.16.degree. 17, and the power supply voltage V.sub.cc2 is applied to the constant voltage diode 19, which becomes conductive. Therefore, transistor 2
1 is turned on and the line 3f becomes "L", the transistor 24 is turned on and the buffers 4a, 4b, 7
．． 10 and resistance 5, 6.8. 9, power supply voltage Vec
l is now supplied, and communication becomes possible.

In this way, in this embodiment, the buffer y provided in the main device 1
4a, 4b, 7.10 and resistors 5, 6, 8.9, and the notification circuit 18 detects whether or not the operating power of the terminal device 2 is at the drive level. When the terminal device 2 is at the drive level, it notifies the main device 1 that the terminal device 2 is in the operating state, and in the main device 1, the transistor 24 of the switch circuit 23 is turned on and off by this operating state notification signal. Buffer y4a serves as a line forming means only when this transistor 24 is in the on state.
, 4b, 7.10 and resistors 5, 6° and 8.9 to establish a communication line.

Therefore, power is supplied to the line forming means in the main device 1 only when the terminal device 2, which is the communication partner, is in an operating state, thereby preventing unnecessary power consumption. This means that power can be saved.

As a result, when no communication is being performed, it is sufficient to turn off the switch 2s of the terminal device 2, and there is no need to turn off the power switch every time the main device 1 is used, allowing work to be carried out smoothly. Further, even if the main device 1 is not used for a long time and the main device 1 is forgotten to be turned off, unnecessary power consumption can be prevented.

Further, since a constant voltage diode 19 is provided in the operating state notification circuit 18, and the transistor 21 is not turned on until the power supply voltage rises to a certain level,
Better power saving is achieved. In addition, in this case, if the normal voltage of power supply voltage Vcc2 is 5v, 4 to 4.5v
It is preferable to select the constant voltage diode 19 so that the transistor 21 becomes conductive at a certain level or higher.

Furthermore, since the operating state notification lines 3f and 3g are at "L" level when the terminal device 2 is in the operating state, the capacitors 29 and 30 are connected to each other as shown by broken lines in FIG.
By providing such a circuit, it can be grounded in an alternating current manner and used for noise prevention, and can be used as a signal return circuit.

Although one embodiment has been described above, the present invention is not limited to this.

For example, although the switch circuit 23 uses a current control transistor as a switching element, it is also possible to use a MOSFET, a relay, or the like.

In addition, when connecting two main devices that can both be used independently, rather than a combination of a main device and a terminal device, an operating state notification circuit and a switch circuit are provided for both.
A similar effect can be obtained by using two operating state notification lines.

Furthermore, in the above embodiment, a case has been described in which power is supplied to the buffer and terminating resistor of the main device 1 only when the terminal device 2 is powered on. For example, if the terminal device 2 is a printer, It can also be used to stop power supply to the buffer and terminating resistor of the main device 1 in response to the stoppage of printing. in this case,
For example, the operating state notification circuit 18 may detect the power supply voltage to the motor that transports the printer head.

〔Effect of the invention〕

As explained above, according to the present invention, power is supplied to the line forming means in one of two devices that communicate with each other only when the other device that is the communication partner is in an operating state. As a result, it is possible to prevent power from being consumed even though it is not necessary, and it is possible to achieve the effect of reducing power consumption. In particular, if applied to a communication system using a parallel transmission method, great effects are expected as the line forming means occupies a large scale.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a line connection circuit according to an embodiment of the present invention, and FIG. 2 is a block diagram schematically showing a data communication system. 1... Main device, 2... Terminal, 3... Cable, 4
... Bidirectional driver/receiver IC, 5, 6... Terminating resistor, 7... Receiver buffer, 10... Driver buffer, 8.9... Terminating resistor, 18... Operating status Notification circuit, 23... Switch circuit, 27...
power supply line.

Claims (1)

[Scope of Claims] A line forming means that is provided in one of two devices that communicate with each other and receives power supply to establish a communication line between the two devices, and the two devices an operating state notification signal line that is connected to the power line of the other device and notifies the one device that the other device is in the operating state when the voltage of the power line is at the drive level; and the other device. a switch means provided in the device and turned on by being driven by the operating state notification signal; and a power supply means supplying the power to the line forming means only when the switch means is in the on state. Line connection circuit.