JPH01500474A - Data communication system with noise reduction means - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] The present invention has a plurality of terminals, a star casilado, and a data base for said terminals. between said star coupler and each one of said terminals for transmitting data. a plurality of bidirectional communication channels connected to the a first transmitter transmitting data from one of said terminals to said star coupler; a second line for transmitting data signals from the star coupler to the terminal; transmission lines, each of said transmission lines connecting said star coupler and said one terminal. a pair of signal wires connected to provide differential signal transmission to and from the The present invention relates to a data communication system consisting of:

This kind of data communication system can be known from US Pat. No. 4,417,334. can. In this system, either terminal sends or sends a signal or message. When transmitting, a star signal is sent from the first transmission line connected to the subsystem. The coupler receives the message and sends the message over each of the second transmission lines. message back to the system. Of course, this system does not send messages The sending subsystem receives messages from local subsystems and sends messages simultaneously. This has the advantage of linking multiple systems because the page is returned. Therefore, this The sending system accepts transmission errors without requesting the receiving subsystem to play the message. You can check the error.

The action of a star coupler is that all signals are originally signal, logically OR the signals on all these first transmit lines, and generated above via a second transmission line of firing to the terminal or subsystem. This is to retransmit the received signal.

Use a star coupler and discuss all of the large signals on the first transmission line in this mode. There are potentially serious problems with If input from the transmission line If the data experiences a high bit error rate, this error can rapidly propagates throughout the system. It is a transmission line from or cooperating with one system. This is especially true if the noise is picked up from.

In the event of a power failure of either terminal processor, failure of the communication line is critical. I found out that

Some noise is transmitted by the terminal processor through the low impedance output of the power supply. Connections to the amplifier continue. Such noise is transmitted through the cable to the star coupler and continues to be transmitted to other stations until detected as an error. and slows down the overall system processing speed.

Disclosure of invention It is an object of this invention to provide a data processing system with reduced noise sensitivity. Ru.

Therefore, according to the invention, each communication channel is connected to system ground. and a shield surrounding said transmission line, each of said terminals having a first transmission line. A differential connected to the wire of the transmission line to transmit data to the line amplification means, said bias voltage means applying a differential voltage to bias said amplification means; a first side of the differential amplifying means and a second side of the differential amplifying means; By doing so, it is possible to isolate the differential amplification means from the system ground. The noise rejection of the star coupler is maintained when no signal is transmitted by To provide a data communication system that allows

Brief description of the drawing Next, one embodiment of the present invention will be described by way of example with reference to the accompanying drawings.

Figure 1 incorporates independent processors, each linked to a star coupler. A simplified block diagram illustrating a data communications system with multiple subsystems. be.

Figure 2 shows how to transmit a signal to a star coupler through a shielded twisted pair. FIG. 3 is a detailed wiring diagram of the transmission amplifier in each subsystem.

FIG. 3 is a detailed wiring diagram of the star coupler receive amplifier.

BEST MODE FOR CARRYING OUT THE INVENTION FIG. 1 is linked by a bidirectional communication channel 14 to a star coupler 16. Data processing system 10 having a plurality of terminals or stations 12 FIG. Stations 12 are numbered 1 to m; Star coupler 1 via channel 14 consisting of 1 and 2 serial transmission lines. Communicate with 6. Each transmission line performs differential signal transmission and is connected by a grounding shield 20. It consists of twisted wire pairs 18 protected by The shield constitutes the lowest potential point of the system Connected to ground or ground 22. Each interactive channel 14 has a stage, The message or serial signal generated from the processor of the line 12 is connected to the star coupler 14. a first transmission line transmitting a message from star coupler 16 or in series to a second transmission line that returns the signal to the subsystem connected to it; Ru.

from the processor transmitter 24 of the stage to the receiver 26 of the star coupler 16. Any message sent or transmitted through one of the transmission lines of - through the transmitter 28 of the coupler 16 and through all second transmission lines; The stage of system 10 that includes the station or subsystem transmitting the message. It will be seen that the signals are transmitted to all engines 1-m. Figures 2 and 3 As can be seen, the transmitter 24.28 and the receiver 26.30 each have a differential amplifier It transmits and receives the necessary differential signals.

The action of the star coupler 16 is for inter-processor communication at all stages. ~m processors are connected together. It is the transmitter 2 of each station 4 and received by the receiver 26 of the coupler, the common link means A logical OR of all signals received by star coupler 16 (not shown) This is achieved by The resulting output signal is transmitted to the wire pair of the second transmission line. from the receiver 30 to the station processor via another transmitter 28. and transmitted.

One problem with this star coupler coupled transmission mode is that either station - Possibility of high bit error communication rates that occur when the processor is powered down It is ability.

Cable, power supply, each stage, communication device 24 and receiver 30, star cabler The shields 14 of all transmitters 28 and receivers 26 of Notice that it is connected to 22. given stage, process When the power to the server goes out, a strange noise is generated from the power supply or other things and goes outside. may be sent to the transmission line wire. If there are no suitable safeguards, The noise is picked up by the receiver 26 of the Star Cobra 16 and becomes active. is connected to the communication channel 14 and sent to the system via linking or means. It will probably spread to

In order to eliminate this problem, especially the power supply VCC3 and a pair of die Ode D1. A circuit 40 consisting of D2 is provided and connects one of the transmitter differential amplifiers 24. Set up a virtual ground connected to the side. The other side of amplifier 24 is a bias power supply. Connected to VNEG and supplies the necessary bias voltage to the transmitter. This virtual grounding cycle By providing ground 40, transmitter 24 is isolated from the common ground of the rest of the system. This occurs when the terminal processor in the stage is powered down. It can cut out the most common noise sources in the Unako system.

The transmitter differential amplifier 24 is connected to the unit WLW2 of the twisted wire pair 18 and is connected to the star Differential signal A to brake 16.

nothing. The output data received on the data line INI, IN2 is sent to the switch Q3, It is connected to the bases of transistors Q6 and Q7 through a differential pair of Q4. Tran The resistor Q6, Q70 pace current is connected to differential switch pair Q3, Q4 and circuit 40. Set by resistors R6 and R7 connected between the set virtual ground point 5o and transistor Q6. Q7 is always kept conductive. transistor Q 5 is a differential transistor pair Q3. Configure a constant current source to provide a reference point for Q4 , transistor Q1. Q2 is for switching transistor pair Q3゜Q4 Configure a circuit to set the reference voltage bias. These transistors are TaQ1. With the threshold point set by Q2, which is more positive than the other? Switch depending on the situation. The threshold point depends on the selection of resistors R2, R3, and R4. Can be changed by adjustment. Diode D3 is the reference bias circuit temperature This is for compensation. Resistors R5 and R8 are standard bias resistors.

A circuit 40 that establishes a virtual ground on one side of the differential amplifier is connected through a voltage dropping resistor R1. and a pair of matched diodes D1. A power supply, typically +5v, connected to D2 Consists of vcc a. In this example, resistor R1 has a voltage of about 0.7 to 0. It is selected to be 8v. Therefore, the voltage drop across DI to ground is approximately 0·,8 It is v.

This voltage drop is matched by choosing a matched diode D2, and its Result node 5o is the direct feed of node 50 to system ground 22. - Maintains a reference level that is equal to the system ground level as a whole, without through connections. held. As a result, a pair of output transistors driving a differential signal into twisted pair 18 Q6. Q7 is a pseudo-noise signal that may be connected through system ground. effectively separated from the issue.

The capacitors C1 and C2 of the virtual ground circuit 40 and the capacitor of the transistor differential amplifier Nocturners C3 and C4 function to account for high and low frequency noise.

Other noise at the terminal when the power goes out is fed through the power supply to twisted pair 18. -Results from packed noise. In order to remove this noise, transistor Q6゜ A balanced differential circuit 7 is connected between the emitter output of Q7 and the bias voltage supply line VNEG. 0 is set. Switched output transistor pair Q6. Q7 is always slightly tar When the power is turned on, a small current flows through R6 and R7, so resistors R9 and RI Connect O. Because of this conduction state and the high capacitance of the transmit channel 14, the resistance R 9°R10 is provided to connect the via from the output limiter of the two transistors Q6 and Q7. It is connected to the power supply line VNEG to reduce its capacitance. This power supply and resistor To prevent noise from being fed back into the twisted pair through the resistor, A diode D5 is connected in series with the resistor R9 and RIO. D6 is provided. The diode is about 50 It has a small forward impedance of ohms, and it has a small forward impedance in normal operation. Provides impedance and does not affect normal transmission. They also represent each equilibrium Total dynamic impedance given by impedance circuit 70.72 selected so that the That is, the resistor R9 and diode D5 are connected in series. The total dynamic impedance presented by the connection is the resistor RIO and the die Total dynamic impedance given by series connection with ode R6 be equivalent to.

As a result, twist! Noise feed in the bias power line ■ field for 18 Pack passage does not occur even when the power of other stations is cut off. deer However, during normal transmission, no variation in the differential output signal occurs.

In FIG. We will discuss other sources of noise that are evident when the cable is turned off. that occurs when a stage, processor, or other similar process is performed. Maybe. In this case, the noise may be caused by the free end of the cable kicking up. do not have. That is, the cable shield is connected at the processor end of the station. This is because the signal is not grounded and is transmitted through the differential amplifier 26 of the receiver. especially , the noise signal is pulled up by the differential amplifier switch pair Q8 and Q9, and the noise signal is boosted up by the differential amplifier switch pair Q8 and Q9. It will be connected to a differential output stage consisting of transistors Qll and Q12. decoupling Even if I use the motherboards C6 and C7, it is still not satisfactory to remove the noise. stomach. Therefore, there is no direct connection between the system ground 22 and the bias power supply line VNEG. Column resistance circuits R11, R12, R13, R14, and R15 are connected.

The use of virtual ground circuit 40 in this transmitter cabinet Start this resistor circuit running from node 22 to independent bias power supply line VNEG 2. - Be able to add it to the coupler cabinet.

This direct connection can be made without the use of this virtual ground circuit 40 at the stage terminal. The column resistor circuit is connected parallel to the R7-Q6 (Figure 2) and R6-Q7 output transistor connections. would appear validly on the line.

The reference value of this resistance may be as follows.

R13-1000 R12-1, OOΩ R14-1000 Ω to R11-3 and 9 Ω to R15-8,2 These resistors maintain the lowest signal-to-noise ratio required for this system. selected and connected to provide a noise rejection offset circuit. noise like this Offset circuits are used specifically when one terminal 12 is removed from the system and the cable is The noise emanating from the free end is picked up and added to the star coupler receiver 26. in cases where it is sent through a width transducer to all other stations in the system. This is important for star coupler coupling structures.

Resistor R13 should match the characteristic impedance of the cable (approximately 96-100 ohms). has a value of 100Ω chosen to %transistor for that matching The quality of the differential signal supplied to the differential amplifier consisting of pair 8 and Q9 is determined by this resistor circuit. It doesn't affect me. Resistors R12 and R14 are connected to the ends of the wire and transistor Q8° It is connected in series between the input of Q9 and the input of the differential amplifier of the receiver in conjunction with R13. Provide a sufficiently high offset voltage between the power terminals. By supplying this resistance Therefore, the differential signal supplied to the input transistor pair Q8゜Q9 of the differential amplifier of the receiver is An offset appears in the number.

This noise offset level voltage is adjusted to match the desired signal-to-noise ratio and 8 wires Wl, W2 are set to be larger than the typical signal noise received. deer However, because these resistors are selected with relatively low matching resistance values, the light during normal signal transmission operation is W1. You can change the differential input signal sent from W2 to transistors Q8 and Q9. It is possible to prevent the generation of such voltage. Resistors R11° and R15 are of high value. Therefore, without attenuating the input signal from the transmission line pair 18, it is possible to connect the bias power supply to ground. The remainder of the circuit in Figure 3 is similar to that in Figure 2. A similar switched differential amplifier receives the signal from the twisted wire pair 18. It is composed of a transistor pair Q8 and Q9. The state of transistors Q8゜Q9 is Which transistor receives the voltage from the current reference transistor QIO to its emitter? Determined by whether the signal applied to its base is more positive than the current reference signal. Ru. Transistor QIO has a low impedance emitter holo at the base of QIO. resistors R19, R20 in conjunction with diode D7 to provide a reference voltage signal; , R21, R22 and transistors Q13°Q14. driven by a reference voltage. Temperature compensation is provided by diode D7 . Resistor R18 is a standard bias resistor. Resistors R16 and R17 are the system graphics Connected between the ground and the base of the output stage transistors Qll and Q12, and a small amount of base current of these transistors at all times during the switching cycle. This prevents the register from being completely blocked.

As can be seen from the above explanation, this invention can remove noise and High bit errors that typically occur when the application processor 12 is powered down A communication circuit with a star coupler coupling structure that minimizes and eliminates were able to provide.

FIG.-1 international search report ANNEX To TIDE INτERNAτl0NAL 5EARC! 4. RE:’ORT 0N INTERNATIONAL A? PLICATrON No, PCT/US 87101666 (SA 180841DEL-A= 2027515 09/12/71 NoneUS"-ni-2188164No n@

Claims (10)

[Claims] 1. A plurality of terminals (12), a star coupler (16) and the star coupler connected between the plug (16) and each one of the terminals (12); multiple bidirectional communication channels (14) for transmitting data to and from the terminal (12); and each of said communication channels (14) is connected to one of said terminals (12). a first communication line for transmitting data from the star coupler (16) to the star coupler (16); - a first transmitting data signal from the coupler (16) to one of said terminals (12); 2 transmission lines, each of said transmission lines being connected to said star coupler (16). and a pair of signals connected between the terminal (12) of said 1 and transmitting a differential signal. A data communication system comprising a wire, each said communication channel (14) having a a shield (20) connected to the stem ground and surrounding the transmission line; each said terminal is connected to a wire of said transmission line and said first transmission line. differential amplifier means (24) for transmitting data to said differential amplifier means (24); 4) bias voltage means for biasing said amplifier means are connected to the first side of said amplifier means; , a virtual grounding means (40) is connected to the second side of said differential amplifier means (24). The differential amplifier means (24) are isolated from the system ground in such a way that When there is no signal transmission from the terminal (12) by separating the A data communication system in which noise rejection of a ter coupler (16) is maintained. 2. The virtual grounding means (40) connects a power source, the bias power source and the system group. The first diode with a set voltage drop connected between the round ( D1) and said first D1 connected to said second side of said differential amplifier means (24). A second voltage drop with a forward set voltage drop matching the voltage drop of the diode (D1). diode (D2), and the potential of the cathode of the second diode (D2) is substantially grounded, but said differential amplifier means (24) is connected to said system ground hand. 2. The system according to claim 1, wherein the system is not connected to a stage. 3. Said differential amplifier means (24) are connected to said transmission line signal wire and said A pair of output transistors (Q 6, Q7) and a data input means for supplying data signals to the differential amplification means (24). stage and a differential connecting the data signal to the pair of output transistors (Q6, Q4). differential means (Q3, Q4) and a temperature compensated bias voltage to said differential means (Q3, Q4). bias means (Q1, Q2, R2 to R5, D3) for supplying the The bias means is connected between the bias voltage means and the virtual ground means (40). The base terminals of the output transistors (Q6, Q7) are connected to the differential means (Q 3, Q4) and to the virtual grounding means (40) through the load resistors (R6, R7). 3. The data communication system according to claim 2, wherein the data communication system is configured to connect. 4. Each said output transistor (Q6, Q7) is connected to said system ground. a collector terminal connected to one of the wires and an emitter terminal connected to one of the wires; data of each of the output ports is transmitted to the star coupler (16). The emitter terminals of the transistors (Q6, Q7) are connected to another balanced impedance is connected to the bias voltage means through the bias circuit (70, 72), and circuit that feeds noise into the transmitting wire when the terminal is powered down. ・Claim 3 includes diodes (D5, D6) polarized to prevent backlash. Data communication system as described in Section. 5. Each said impedance circuit (70, 72) is an emitter terminal of said transistor. a resistor with the diode connected in series between the bias voltage means and the bias voltage means; The diodes (D5, D6) are connected to the impedance circuit (70, 72). The diode dynamic impedance and resistance are chosen to be equal. The system described in item 4. 6. The virtual grounding means (40) is connected between the power supply and the system ground. Claims comprising capacitive means (C1, C2) connected to reduce high and low frequency noise The system described in box 3. 7. connected between the bias voltage means and the virtual ground means (40); Claim 6 comprising second capacitive means (C4, C5) for reducing low frequency noise. system. 8. The star coupler (16) is connected to the signal wire of the first transmission line. a second differential amplifying means (26) having two inputs; means (26) receive at said star coupler (16) of said first transmission line; the first transmission to the star coupler (16) to amplify the data; the second bias voltage hand has two inputs connected to the signal wires of the line; A stage is connected to a first side of said second differential amplification means (26) and is connected to said system group. round is connected to the second side of said second differential amplifier means (26) and said noise Rejection means is configured to provide a voltage from said second bias voltage means to said two differential amplifier inputs. 2, including a resistor circuit (R11 to R15) connected to the system ground. By setting the noise offset voltage on two inputs, the noise offset level voltage is the wires that meet the desired signal-to-noise ratio at the second differential amplifier input are received; The system according to claim 1, wherein the noise is set to be louder than the typical noise. . 9. The resistor circuit is connected between two inputs of the second differential amplification means (26). and has a value approximately equal to the characteristic impedance of the communication channel (14). 1 resistor (R13), and a resistor (R13) between one of the inputs and the second bias voltage means. and the first resistor connected between the other of the inputs and the system ground. A claim including second and third resistors (R11, R15) having a higher value than the resistor (R13) The system according to item 8. 10. The resistor circuit has approximately the same value as the first resistor (R13), and 2 of the differential amplification means (26) and in series with the wire of the first transmission line. Claim 9 includes fourth and fifth resistors (R12, R14) connected to system.