JPH04245817A - Data reception circuit - Google Patents

Abstract

PURPOSE:To detect the disconnection of power supply or a connector of a transmitting side by providing a level detecting part by connecting a terminal resistor between the input terminals of a differential amplifier to receive the data of a pseudo ECL level, and connecting an earthing resistor between each input terminal and the earth. CONSTITUTION:At the time of operating in a normal state, the data of the false ECL level is transmitted from a transmission circuit 7 to a balanced transmission line 1, and the level detecting part 6 decides the transmission line to be normal. In the case of the disconnection of the power supply or a cable at a transmission circuit 7 side, since the earthing resistors 4, 5 are connected to the input terminal of the differential amplifier 2, the transmission line falls lower than the pseudo ECL level, for instance, to an earth level. This fall of the level is detected by the level detecting part 6, and an alarm signal can be outputted. Besides, in the case that a large in-phase noise is introduced to the balanced transmission line 1, the level of one line of the balanced transmission line 1 falls sometimes lower than the pseudo ECL level. Since the fall of the level in this case is not continuous, the alarm signal is prevented from being outputted by providing an integration circuit.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data receiving circuit that receives data transmitted at a pseudo ECL level. 2. Description of the Related Art A system is known in which devices are connected by a balanced transmission line and data is transmitted in a balanced manner. The data receiving circuit in such a system receives and detects data from a balanced signal transmitted through a balanced transmission line using a differential amplifier, and is composed of a TTL (transistor-transistor-logic) circuit. Common. If it is necessary to transmit data at even higher speeds, an ECL (emitter coupled logic) circuit capable of high speed operation is used. Since this ECL circuit requires at least two power supplies, a pseudo ECL circuit that can operate with one power supply like a TTL circuit is sometimes used. For example, the TTL level is 2.7V for high level and 0.5V for low level.
The ECL level is, for example, -0.8V for high level and -1.8V for low level. On the other hand, the pseudo-ECL level is
The level is shifted by approximately +5V, with the high level being +4V and the low level being +3V. Such a pseudo E
There is a demand for a data receiving circuit using a CL circuit to be able to detect power failure or cable disconnection on the transmitting side with a simple configuration.

0002

2. Description of the Related Art When transmitting data between conventional devices, for example, the configuration shown in FIG. 5 is known. In the figure, A and B are various devices such as a central processing unit, input/output device, and channel control device, 31 is a balanced transmission line, 32 is a differential amplifier, 33 is a terminating resistor, and 34 and 35 are grounding resistors. , 37 is a transmitting circuit, 38 and 39 are connectors, 40 is an AND circuit,
41 is a balanced transmission line; 42, 43, and 44 are resistors; 45 is a transmission circuit; and 46 is a differential amplifier. Data is transmitted by circuit 3
7 as a balanced signal from the device A to the device B via the balanced transmission path 31, and received by the differential amplifier 32 that constitutes the receiving circuit of the device B.

When this transmitting circuit 37 has a pseudo ECL circuit configuration, grounding resistors 34 and 35 are connected as pull-down resistors to the output terminal side of the transmitting circuit 37, and a terminating resistor 33 is connected between the input terminals of the differential amplifier 32 of the receiving circuit. are connected, and as described above, data is transmitted using a balanced signal of high level and low level of +4V and +3V. In this case, even if the input to the differential amplifier 32 is cut off due to power cut off of the transmitting circuit 37, disconnection of the connectors 38 and 39, breakage of the balanced transmission line 31, etc., a differential signal due to induced noise etc. is input. In some cases, incorrect data that is not legitimate data is sent.

Therefore, in order to detect power failure on the transmitting circuit 37 side, disconnection of the connectors 38 and 39, disconnection of the balanced transmission line 31, etc., the transmitting circuit 45 of the TTL circuit configuration, the balanced transmission line 41, and the differential amplifier 46 are connected. A configuration is provided, and a transmitting circuit 45
The input of the transmitter circuit 45 is grounded and set to low level, and under normal conditions, the non-inverting output terminal of the transmitting circuit 45 is at low level and current flows in, and the inverting output terminal is at high level and current flows out.
The level of the + terminal of the differential amplifier 46 is higher than that of the - terminal, and the output becomes high level. Therefore, the data received by the differential amplifier 32 is outputted via the AND circuit 40. If the power is cut off or the connectors 38 and 39 are disconnected, the level of the + terminal of the differential amplifier 46 will be lower than that of the - terminal, so the output will be at a low level, and the AND circuit 40 will be closed and the differential amplifier 32 will be disconnected. Sending of a definitive output signal is prevented.

FIG. 6 shows the main parts of the transmitting circuit having the above-mentioned pseudo-ECL circuit configuration, in which Q1 to Q4 are transistors, R1 and R
2 is a resistor, IN is an input terminal for transmission data, OUT1, O
UT2 indicates a non-inverting output terminal and an inverting output terminal, and Vr indicates a reference voltage. When a high level signal is input to the input terminal IN, the non-inverting output terminal OUT1 has an output voltage of about +4V, and the inverting output terminal OUT2 has an output voltage of about +3V. Therefore, both in the case of a high-level output and in the case of a low-level output, current flows to the balanced transmission line side.

[0006] For example, as shown in FIG. 7, a receiving circuit for receiving such pseudo-ECL level data has transistors Q5 and Q6, resistors R3 to R10, and a logic circuit 51. Differential amplifier 32
is configured, and the non-inverting output terminal OUT of the transmitting circuit is connected via the input terminals IN1 and IN2 and the balanced transmission line 31.
1 and the inverting output terminal OUT2 are connected. When power is cut off on the transmitting side or the connectors 38 and 39 are disconnected, the input level difference between the input terminals IN1 and IN2 becomes zero, and only the fluctuation due to the noise component remains, and the output signal that considers the fluctuation as the input signal is It will be added to the logic circuit 51,
Incorrect data will be output from the output terminal OUT. In order to prevent such drawbacks, a detection configuration is provided as shown in FIG.

[0007] Furthermore, the transmitting circuit having a TTL circuit configuration is, for example,
As shown in FIG. 8, the non-inverting output terminal side has transistors Q7 and Q8, a diode D1, and a resistor R11. When the transistor Q7 is turned on and the transistor Q8 is turned off, the output terminal OUTT is connected to the resistor R11 and the transistor Q7.
, the voltage drop due to the diode D1 becomes approximately +3.5V, and the current IH flows out to the balanced transmission line as shown by the solid line. Further, when the transistor Q7 is turned off and the transistor Q8 is turned on, the output terminal OUTT becomes approximately 0.4V due to the voltage drop of the transistor Q8, and the current IL flows from the balanced transmission line as shown by the dotted line. Therefore, by the resistors 42, 43, 44 and the differential amplifier 46 in FIG. 5, it is possible to detect power failure on the transmitting side, disconnection of the connectors 38, 39, etc.

[0008]

[Problem to be solved by the invention] As mentioned above, ECL
The circuit configuration has the advantage of being able to operate at high speed, but ECL
In order to transmit the level, there is a drawback that multiple power supplies are required, and therefore, a pseudo ECL circuit configuration that can be driven by a single power supply, for example, +5V power supply is adopted. In that case,
As shown in FIG. 5, it is not possible to detect power failure on the transmitting circuit 37 side, disconnection of the connectors 38, 39, etc., so a transmitting circuit 45 for detection, a balanced transmission line 41, and a differential amplifier 46 as a receiving circuit must be provided. However, this has the drawback of increasing the size of the device. SUMMARY OF THE INVENTION An object of the present invention is to enable easy detection of power outage and connector disconnection on the transmitting side in the case of balanced transmission at a pseudo ECL level using a simple configuration.

[0009]

[Means for Solving the Problems] The data receiving circuit of the present invention will be described with reference to FIG. In a receiving circuit that receives data transmitted at a pseudo ECL level through this balanced transmission line 1, a terminating resistor 3 is connected between the input terminals of a differential amplifier 2, and the differential amplifier 2 Grounding resistors 4 and 5 are connected between each input terminal of the balanced transmission line 1 and the ground, and a level detection unit 6 is connected to detect whether the level of at least one line of the balanced transmission line 1 is lower than the pseudo ECL level. This is what I did.

The level detecting section 6 is configured to output an alarm signal indicating that the transmitting side power is cut off or the cable is disconnected when the potential of at least one of the balanced transmission lines 1 reaches the ground level. Furthermore, an integration circuit is connected to the level detection section 6.

[0011]

[Operation] Under normal conditions, pseudo-ECL level data is sent from the transmitting circuit 7 to the balanced transmission line 1, so the differential amplifier 2
Even if the grounding resistors 4 and 5 are connected to the input terminals of , the level detecting section 6 will determine that it is normal because the pseudo ECL level will be obtained. In the case of power failure or cable disconnection on the transmitting circuit 7 side, since the grounding resistors 4 and 5 are connected to the input terminals of the differential amplifier 2, the level becomes lower than the pseudo ECL level, for example, at the ground level. This level drop can be detected by the level detection section 6 and an alarm signal can be output. Further, when large common-mode noise is induced in the balanced transmission line 1, the level of either line of the balanced transmission line 1 may fall below the pseudo ECL level. Since the level drop in this case is not continuous, an integrating circuit is provided to prevent the output of an alarm signal, and in the case of a continuous level drop, an alarm signal is output.

0012

[Embodiment] FIG. 2 is an explanatory diagram of an embodiment of the present invention.
1 is a balanced transmission line, 12 is a differential amplifier, 13 is a terminating resistor,
14 and 15 are grounding resistors, 16 is a gate circuit that constitutes a level detection section, 17 is a transmitting circuit, 18 and 19 are connectors,
20 is an AND circuit. A terminating resistor 13 is installed between the +input terminal and the -input terminal of the differential amplifier 12 constituting the receiving circuit.
, ground resistors 14 and 15 are connected between the +input terminal and the -input terminal connection and the ground, respectively, and a gate circuit 16 is connected to the -input terminal. Therefore, the current caused by the pseudo ECL level output signal of the transmitting circuit 17 flows from the balanced transmission line 11 to the ground via the grounding resistors 14 and 15.

The transmitting circuit 17 of the device A has the configuration shown in FIG. 6, for example, and sends out a balanced signal at a pseudo ECL level to the balanced transmission line 11, and includes a differential amplifier 12 constituting the receiving circuit of the device B. Pseudo E is connected to the + input terminal and - input terminal of
A balanced signal at CL level is input. The gate circuit 16 outputs a high level signal in response to an input equal to or higher than the pseudo ECL level, and thereby the output of the differential amplifier 12 is sent out as received data via the AND circuit 20.

[0014] Also, if the power is cut off on the transmitting circuit 17 side, the connector 18
, 19, disconnection of the balanced transmission line 11, etc., the + and - input terminals of the differential amplifier 12 are connected to the ground resistor 14,
15 to the ground level. In other words, it will be lower than the pseudo ECL level. Therefore, the output signal of the gate circuit 16 becomes low level, the AND circuit 20 is closed, the output of the differential amplifier 12 is blocked, and a low level alarm signal is output.

FIG. 3 is an explanatory diagram of another embodiment of the present invention, in which a comparator 21 is provided as the level detection section 6, and the same reference numerals as in FIG. 2 indicate the same parts. The comparator 21 compares a reference voltage 22 with the level of one line of the balanced transmission line 11, and this reference voltage 22 is selected to have a value lower than the pseudo ECL level. Therefore, under normal conditions, the output signal of the comparator 21 is at a high level, and the AND circuit 2
0 is opened and the output of differential amplifier 12 is sent out as received data. Also, power off on the transmitting circuit 17 side, connector 1
8, 19 or a break in the balanced transmission line 11, the level of the balanced transmission line 11 becomes below the pseudo ECL level, so the output signal of the comparator 21 becomes low level, and the AND circuit 20 is closed. Additionally, a low level alarm signal is sent out.

FIG. 4 is an explanatory diagram of still another embodiment of the present invention, in which an integrating circuit 24 is provided on the output side of the level detecting section 23, and the same reference numerals as in the other FIGS. 2 and 3 are the same. Show parts. The output signal of the level detection unit 23 consisting of the gate circuit 16, comparator 21, etc. described above is such that when large common-mode noise is induced in the balanced transmission line 11, the level of the balanced transmission line 11 randomly decreases below the pseudo ECL level. There are things to do. Since such a random low-level output signal becomes a continuous high-level signal by the integrating circuit 24, a low-level alarm signal is not sent out, and the AND circuit 20 remains open. It will be. In the case of a power failure on the transmitting circuit 17 side, a cable disconnection, etc., the output signal of the level detection section 23 will continue to be at a low level, so the output signal of the integrating circuit 24 will also continue to be at a low level, and an alarm signal will be signaled. It will be sent out.

[0017]

Effects of the Invention As explained above, the present invention provides pseudo E
A terminating resistor 3 is connected between the input terminals of a differential amplifier 2 that receives CL level data, grounding resistors 4 and 5 are connected between each input terminal and the ground, and a level detecting section 6 is provided. Yes, the level of balanced transmission line 1 will maintain the pseudo ECL level during normal operation when pseudo ECL level data is being sent from the transmitting circuit 7, but if the power is cut off on the transmitting circuit 7 side or the cable is disconnected. In this case, the level of the balanced transmission line 1 is below the pseudo ECL level, which is detected by the level detector 6 and an alarm signal is sent out.
High-speed operation is possible using the L circuit configuration, and power failure or cable disconnection on the transmitting circuit 7 side can be detected without providing a detection transmission line or transmitting/receiving circuit, so the configuration of the receiving circuit can be simplified. There are advantages.

Furthermore, as shown in FIG. 4, by providing an integrating circuit in the level detection section, malfunctions due to noise etc. are prevented, and the reliability of the detection operation of power failure or cable disconnection on the transmitting circuit 7 side is improved. There are advantages to being able to do so.

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining the principle of the present invention.

FIG. 2 is an explanatory diagram of one embodiment of the present invention.

FIG. 3 is an explanatory diagram of another embodiment of the present invention.

FIG. 4 is an explanatory diagram of still another embodiment of the present invention.

FIG. 5 is an explanatory diagram of a conventional example.

FIG. 6 is a circuit diagram of a main part of a transmitting circuit having a pseudo ECL circuit configuration.

FIG. 7 is a circuit diagram of a main part of a receiving circuit having a pseudo ECL circuit configuration.

FIG. 8 is a circuit diagram of a main part of a transmitting circuit having a TTL circuit configuration.

[Explanation of symbols]

1 Balanced transmission line 2 Differential amplifier 3 Terminating resistor 4,5 Ground resistance 6 Level detection section 7 Transmission circuit 8,9 Connector

Claims (3)

[Claims] Claim 1: In a data receiving circuit including a differential amplifier (2) that receives data transmitted at a pseudo ECL level through a balanced transmission line (1), a A terminating resistor (3) connected, a grounding resistor (4), (5) connected between each input terminal of the differential amplifier (2) and ground, and a terminal resistor (4), (5) connected to the differential amplifier (2). A data receiving circuit comprising: a level detecting section (6) for detecting whether the level of at least one line of the balanced transmission line (1) is lower than the pseudo ECL level. 2. The level detection unit (6) outputs an alarm signal as a result of a power cut on the transmitting side or a cable disconnection when the potential of at least one of the balanced transmission lines (1) reaches approximately the ground level. 2. The data receiving circuit according to claim 1, wherein the data receiving circuit has a configuration. 3. The data receiving circuit according to claim 1, wherein an integrating circuit is connected to the level detecting section (6).