JPH07182082A - Interface device - Google Patents

Abstract

PURPOSE:To provide more efficient fail-safe at a low cost. CONSTITUTION:In this interface provided with output side and input side interface connecters, a line driver 1 and a line receiver 2 connected to them and an interface cable 7 for attachably and detachably connecting the interface connectors on the output side and on the input side, a means for supplying enable signals to at least one of the line driver 1 and the line receiver 2 from the other side by a wiring route 51 provided through the interface connectors on the output side and on the input side and the interface cable 7 or the means for supplying such enable signals from the side where they are supplied by the wiring route provided through the interface connector on the side and the interface cable 7 while being folded back inside the interface cable 7 is provided and the line driver 1 or the line receiver 2 is turned to a non-active state when the wiring route is disconnected and the supply of the enable signals is stopped.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an interface device for transmitting data from a device to another device.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 2, in a fail-safe circuit in an interface device, when a differential input line receiver 2 is used, a series resistor and pull-up / pull-down resistors 103 and 105 are placed after a terminating resistor 6. When the cable 7 is inserted and the cable 7 is detached, a potential difference of the differential voltage is generated. In the fail-safe in this case, when the transmission line is short-circuited, disconnected, the connector is disconnected, or the like, the output enters an indefinite region below the input threshold level of the differential input line receiver, and the output becomes indefinite.

Further, as shown in FIG. 3, a fail-safe can be realized by connecting a capacitor 107 to the terminating resistor 6, but the capacitor 107 affects the transmission characteristics and therefore can be used only for low speed.

[0004]

However, in the conventional example shown in FIG. 2, the pull-up resistor 103 and the pull-down resistor 105 are used to keep the input of the differential input line receiver 2 constant. was there.

(1) Since current flows through the terminating resistor 6 and the pull-up resistor 103 and the pull-down resistor 105, power consumption increases.

(2) Since an external resistor is used, the number of parts is increased and the cost is increased. There is a method of inserting a capacitor at a place where a terminating resistor is inserted instead of the pull-up resistor and the pull-down resistor, but the transmission characteristic becomes slow because the capacitor affects the transmission characteristic.

An object of the present invention is to realize a more efficient and low cost fail safe in an interface device in view of the problems of the prior art.

[0008]

In order to achieve this object, according to the present invention, an output side interface connector, a line driver connected thereto, an input side interface connector, a line receiver connected thereto, and the output side and In an interface device including an interface cable that detachably connects between input-side interface connectors, an enable signal for at least one of the line driver and the line receiver is sent from the other side to the output-side and input-side interface connectors. And a means for supplying by a wiring path provided via the interface cable, and the line driver or line receiver on the at least one side stops supplying the enable signal when the wiring path is cut off. Characterized in that it is made of a non-active state. Alternatively, instead of said supply means, an enable signal is supplied from the side to which it is supplied.
There may be provided a means for supplying via the interface connector on that side and the interface cable and by a wiring route provided by folding back inside the interface cable.

When the line receiver becomes inactive, the line receiver sets its output signal line in a high impedance state, for example. In that case, it is preferable to have a means for electrically pulling up or down the output signal line of the line receiver through a resistor.

[0010]

In this structure, the interface cable is connected to the output-side and input-side interface connectors, and if there is no disconnection in the interface cable, the enable signal is supplied to the line driver or the line receiver through the wiring path. , The interface device works normally. When the interface cable is removed from the interface connector or the interface cable is broken, the wiring route is cut and the supply of the enable signal is stopped, and the line driver and the line receiver are deactivated. Thus, fail safe is achieved. At that time, power consumption through the terminating resistor as in the case of the conventional example of FIG.
There is no influence on the transmission characteristics by the capacitor as in the case of the conventional example.

[0011]

【Example】

(Embodiment 1) FIG. 1 is a circuit diagram showing an interface device according to a first embodiment of the present invention. As shown in the figure, this device has an output side interface connector (not shown),
A differential line driver 1 connected to this, an input side interface connector (not shown), a differential line receiver 2 connected to this, an interface cable 7 for detachably connecting between the output side and input side interface connectors. Means for supplying enable signals to the differential line driver 1 and the differential line receiver 2 from the other side through the wiring path 51 provided via the interface connectors on the output side and the input side and the interface cable 7, respectively. The differential line driver 1 and the differential line receiver 2 become inactive when the wiring path 51 is cut off and the supply of the enable signal is stopped. 3 is an enable signal input terminal of the differential line driver 1, 4 is an enable signal input terminal of the differential line receiver 2, 8 is an interface reception signal line connected to the output side of the differential line receiver 2,
5 is a pull-up resistor connected to this, 9 is an interface transmission signal line connected to the input side of the differential line driver 1, 10 is a differential output terminal (+), 11 is a differential output terminal (-), 12 is a differential input terminal (+), 13 is a differential input terminal (-), 6 is a terminating resistor connected between the differential input terminals 12 and 13, and 14 and 15 are enable terminals connected to the wiring path 51. Ground signals, 16 and 17 are pull-up resistors connected to the wiring path 51, and 30 is a ground signal line.

Here, when the interface signal cable 7 is connected to the input side and output side interface connectors, the enable signal input ends 3 and 4 are connected to the ground signals 14 and 15 through the wiring path 51, so that the differential signal is transmitted. The line driver 1 and the differential line receiver 2 are enabled. As a result, the interface transmission signal 9 is correctly transmitted as the interface reception signal 8.

When the interface cable 7 is removed, the enable signal input terminals 3 and 4 are disconnected from the ground signals 14 and 15, and the pull-up resistor 16 is connected.
“High” is input from and 17. As a result, the differential line driver 1 and the differential line receiver 2 are disabled, and especially the differential line receiver 2
Is set to "high" by the pull-up resistor 5 in order to bring the interface reception signal line 8 into a high impedance state.
Will be output.

In this way, when the interface cable 7 is removed, the interface reception signal 8 is always "high" and stable, and does not enter an indefinite state. (Embodiment 2) FIG. 4 shows a second embodiment of the present invention. This is applied to bidirectional communication by adding a differential line driver 19 and a differential line receiver 18 in addition to the differential line driver 1 and the differential line receiver 2.

Also in this embodiment, when the interface cable is removed, the interface reception signal lines 8 on both sides are always "high" and stable, and the indefinite state does not occur. (Embodiment 3) FIG. 5 shows a third embodiment of the present invention. This is obtained by adding a non-differential single-ended line driver 20 and a single-ended line receiver 21 to the embodiment of FIG.

Also in this case, as in the previous example, if the interface cable 7 is connected, communication can be carried out normally, and by removing the interface cable 7, not only the differential line receiver 2 but also the enable signal line of the normal line receiver 21 can be used. Also becomes the disenable state, and the output of the line receiver 21 becomes high impedance and becomes “high” by the pull-up resistor 22. As a result, it can be seen that even when combined with the normal line driver 20 and line receiver 21, the respective reception signal lines 8 and 88 become “high” and stable when not connected. (Embodiment 4) FIG. 6 shows a fourth embodiment of the present invention. This is because the wiring paths 51 to the enable signal ends 3 and 4 of the line driver 1 and the line receiver 2 loop back in the interface cable 7 and are connected to the ground on the same side, respectively. In the figure, 31 and 32 are loopback signal lines in the interface cable 7. Accordingly, when the connector of the interface cable 7 is removed, the line driver 1 or the line receiver 2 on the connector side can detect that the cable is removed.

The feature of this case is that the ground levels on the line driver side and the line receiver side do not have to be matched. However, even if the cable 7 is disconnected,
Only the line driver 1 or the line receiver 2 on the removed side can detect the removal.

[0018]

As described above, according to the present invention, fail-safe can be achieved without the conventional power consumption through the terminating resistor and the influence of the capacitor on the transmission characteristics. Further, by providing a means for pulling up or pulling down the output signal line of the line receiver, it is possible to prevent malfunction due to detachment of the cable.

Further, since the pull-up and pull-down resistors can be reduced in the transmission / reception devices on the line driver side and the line receiver side, respectively, the power consumption can be kept low.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an interface device according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing a conventional interface device.

FIG. 3 is a circuit diagram showing another conventional interface device.

FIG. 4 is a circuit diagram showing an interface device according to a second embodiment of the present invention.

FIG. 5 is a circuit diagram showing an interface device according to a third embodiment of the present invention.

FIG. 6 is a circuit diagram showing an interface device according to a fourth embodiment of the present invention.

[Explanation of symbols]

1, 19: differential line driver, 2, 18: differential line receiver, 6: terminating resistor, 7: interface cable, 8, 88: received signal line, 3, 4: enable signal input end, 5, 22: pull Up resistance, 9: transmission signal line, 1
0: Differential output terminal (+), 11: Differential output terminal (-),
12: differential input terminal (+), 13: differential input terminal (-), 14 and 15: ground signal, 16 and 17: pull-up resistor, 20: line driver, 21: line receiver, 30: ground signal line , 31, 32: loopback signal lines, 51: wiring route.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tatsuya Sakashita 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Kenichiro Ono 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Incorporated (72) Inventor Masami Shimakura 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Morimoto Hajime 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. ( 72) Inventor Takeshi Hasegawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (4)

[Claims] 1. An output side interface connector, a line driver connected thereto, an input side interface connector, a line receiver connected thereto, and an interface cable for detachably connecting the output side and input side interface connectors. In the interface device including the above, an enable signal for at least one of the line driver and the line receiver is supplied from the other side through a wiring path provided through the interface connector on the output side and the input side and the interface cable. Have the means to
The interface device, wherein the line driver or the line receiver on at least one side becomes an inactive state when the supply of the enable signal is stopped due to the disconnection of the wiring path. 2. An output side interface connector, a line driver connected thereto, an input side interface connector, a line receiver connected thereto, and an interface cable for detachably connecting the output side and input side interface connectors. In an interface device including, an enable signal for at least one of the line driver and the line receiver is returned from the other side through the interface connector on the other side and the interface cable, and folded back within the interface cable. The line driver or line receiver on at least one side is provided with an inactive state when the supply of the enable signal is stopped due to the disconnection of the wiring route. An interface device characterized in that 3. The interface device according to claim 1, wherein when the line receiver is in an inactive state, the line receiver puts its output signal line into a high impedance state. 4. The interface device according to claim 3, further comprising means for electrically pulling up or pulling down the output signal line of the line receiver through a resistor.