SU1645962A1 - Device for user interfacing to local computer network communication line - Google Patents

Abstract

The invention relates to computing and can be used in computer networks of local networks for exchanging messages over a common backbone line of IBM and network subscribers. The purpose of the invention is to increase the reliability of the device. The goal is achieved by the fact that a device for analyzing a communication line, two blocks of time line, are inserted into the device containing the communication line, the line matching unit, the transmitter, the receiver, the bpok of forming the communication line state interrogation pulse, the AND element and the OR element. signal selection by duration and block information subscriber output. 3 ep f-ly, 9 ill.

Description

The invention relates to computing and can be used in local area networks of computers designed to exchange messages over a common trunk line between computers and network subscribers.

The purpose of the invention is to increase the reliability of the device "

FIG. 1 is a block diagram of the device; Fig. 2 is a block diagram of a link state analysis block; in fig. 3 - block diagram of the time signal selection for the duration; in fig. 4 is a block diagram of the blocking information subscriber output; on league. 5 shows a circuit for forming a polling pulse of a communication link; on league. 6 is a transmitter diagram; in fig. 7 is a receiver diagram; in fig. 8 is a diagram of the matching unit

with a line; in fig. 9 shows time diagrams of operation of the device with signals at the outputs of the corresponding elements, dashed lines show the situation of the collision of interrogation pulses, in which the transmission permission signal is not generated.

The device contains a communication link matching unit 1, a transmitter 2, a receiver 3, a link state analysis block 4, a first signal duration block 5, a second duration block 6, a duration element SEL 7, a pulse shaping block 8 interrogation of the state of the communication line, the AND 9 element, the node 10 of blocking the information subscriber output, the trunk line (channel) 11 of the communication, the inert subscriber input 12, inLorma0 4 SL

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subscriber output 13, input 14 transmission requests, output 15 transmission permission.

To the trunk two-wire communication line 11 are connected according to the circuit of a multi-point device, similar to the one proposed.

The 4-link state analysis unit consists of the triggers 16 and 17 and the optocoupler nodes 18 and 19.

Blocks 5 and 6 of the signal time selection include the key 20, the integrator 21, the constant reference source 22 and the threshold element 23 „

The node 10 blocking information subscriber output is made on the trigger 24 and the element OR 25,

The pulse shaping unit 8 of the communication link state circuit consists of a trigger 26, single vibrators 27 and 28, and a strobing pulse generator 29.

Transmitter 2 comprises an optical disconnect node 30 and a key 31, receiver 3 a comparator 32, and an optical isolator node 33.

The line matching unit 1 is made on a controlled current generator 34 and a decoupling amplifier 35.

The unit 4 for analyzing the state of the communication line is designed to monitor the state of line 11 after the end of the interrogation pulse transmitted to it and the Forgera 16. If at the moment of line fixation

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11 is unavailable, then at the input of the trigger 16 there is 1, the trigger 16 switches to the one state. If line 11 is occupied, then 0 is present at the input of trigger 16, the zero state of trigger 16 does not change at the time of polling.

The very first switching of the trigger 16 to a single state causes the switching of the trigger 17 to a single state, which is maintained even if the trigger 16 for some reason switches again to a zero state for some time (for example, due to its inputs of short impulse noise) "Thus, the trigger 17, performed the trigger latch function, reliably captures the detected free state of line 11, forming at its output a signal to enable transmission until the end of the signal. Transmission request at output 14 of the device properties. The optocoupler nodes 18 and 19 allow the immunity of unit 4 to be increased, since they make it possible to electrically separate (from the inputs, outputs and common wires of the power supply circuits) the elements and electrical circuits of the device connected directly to the communication line 11, connected with logic elements and common wire of computer power supply circuits and signal subscription. Allow transmission of 35 t of network. In the absence of galvanic 1645962

Hera 16. If at the time of fixing the line

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11 is unavailable, then at the input of the trigger 16 there is 1, the trigger 16 switches to the one state. If line 11 is occupied, then 0 is present at the input of trigger 16, the zero state of trigger 16 does not change at the time of polling.

The very first switching of the trigger 16 to a single state causes the switching of the trigger 17 to a single state, which is maintained even if the trigger 16 for some reason switches again to a zero state for some time (for example, due to its inputs of short impulse noise) "Thus, the trigger 17, performed the trigger latch function, reliably captures the detected free state of line 11, forming at its output a signal to enable transmission until the end of the signal. Transmission request at output 14 of the device properties. The optocoupler nodes 18 and 19 allow the immunity of unit 4 to be increased, since they make it possible to electrically separate (from the inputs, outputs and common wires of the power supply circuits) the elements and electrical circuits of the device connected directly to the communication line 11, connected with logic elements and common wire of computer power supply circuits and subscriber of the network. In the absence of galvanic

chi, if the line at the time of the survey is free.

Before the device starts operating, before a signal appears, the transfer request at the device input 14 and the first input of block 4 triggers 16 and 17 are blocked and are in the initial zero state. The appearance of a signal Transmission request in the form of 1, coming through the node 18 of the optocoupler, unlocks the triggers 16 and 17.

After the transmission to the link 11 of the interrogation pulse is completed, it is sent from the additional output of the transmitter 2 through the time selection block 5 to the trigger input of the trigger 16. At the trigger 16, the back (positive) front of this pulse from the output of block 5 fixes 40

45

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The isolation between the indicated elements and the circuits along the common ground wire of the device is well transmitted by various impulse interferences generated by switching logic elements, in addition, in this case, interferences can also occur due to the differing values of the potential difference between the communication lines and common ground wire from different network subscribers.

Blocks 5 and 6 have different values of the selection time interval during which the formation of the output signal is delayed.

Unit 5 is designed to delay the back (positive) edge of interrogation pulses, which in trigger 1 are synchronized with the state of the line displayed on the video link as well as the logical value of the (zero or single) signal coming from receiver output to input trig0

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The isolation between these elements and the circuits along the common ground wire of the device is well transmitted by various impulse noise generated by switching logic elements, and in this case, interference can also occur due to different values of the potential difference between the communication lines and the common ground wire from different network subscribers.

Blocks 5 and 6 have different values of the selection time interval during which the formation of the output signal is delayed.

Unit 5 is designed to delay the back (positive) edge of the interrogation pulses, which in the trigger 16 are synchronized with the state of the communication line, and also designed to filter out possible short impulse noise. The time interval for the selection of block 5, the value of which

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the rear (positive) edge of the interrogation pulse is delayed, is chosen equal to the interrogation pulse propagation delay time by the following electrical circuit: unit output 3 - element 7 - transmitter 2 - unit 1 - receiver 3 - trigger input 1b "Selecting such a selection time value reliably Record line conditions only after the end of the transmitted polling pulse.

Unit 6 is designed to detect an unoccupied link state (no signals in the line) in the event that the time interval between adjacent consecutive signals in the line is set to the value of the selection time interval. The time interval for selection of block 6 is chosen to be equal to ZTR, where T "is the time of signal propagation along the communication line from its beginning to the end

In the initial state (in the absence of selectable signals), the input of block 5 or 6 of the time selection receives the level O, which keeps key 20 in a closed state, bypassing the integrator's output 21 o At the moment of the appearance of the selectable signal, key 20 is opened, and shunting is removed the output of the integrator 21 and the integration of the reference voltage of the source 22 begins during the lifetime of the input signal. The time constant of the integrator determines the time interval for the selection of blocks 5 and 6, which is equal to the time interval between the moment when the key 20 is unlocked and the time when the integrator 21 reaches a rising voltage, the threshold level of the trigger voltage of the threshold element 23.

The node 10 is designed to block the information subscriber output of the device for a period from the moment of detection of an unoccupied line condition until the end of the received interrogation pulse. This allows you to exclude a special pulse of polling the line condition from the received sequence of modulated information signals, as well as to filter out individual impulse noise in the one state blocking the passage of signals through the OR 75 element, trigger 24 is set by signal level

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in the form of 1, coming from the output of block 6 of the time selection in the case of the absence of line 11 by signals from other network subscribers. The initial zero state of the trigger 24 is set by the synchronous input (by recording O) by the rear (positive) front of the received interrogation pulse coming from the output of receiver 3.

Due to the presence of the node 10 blocking on the information subscriber output 13 of the device as well as on the information subscriber input

12 Only modulated information signals are present. Blocking information subscriber output

At the time of the free state of the link 11 detected by the unit 6, it is possible to filter out some rare impulse noise arising in an unoccupied line of communication from various external electromagnetic disturbances, and to slightly increase the noise immunity of the entire device.

Block 8 serves to generate a polling pulse of the link state. Before the device starts operating, before the signal 1 appears at the input 14 of the transfer request, the output of the block 8 is blocked, since the trigger 26 on the reset input is kept in its initial state by the level O received from input 14 devices. Signal Appearance - A transmission request in the form of 1 transfers block 8 to the start-up state from element 9. When a start signal is received from block 8, the single-vibrator 27, which performs the function Q of the delay element, generates a pulse that delays the beginning of the generation of the interrogation pulse by the time is longer than the scatter time of the response of the time selection blocks 6 for different network subscribers. The impulse generated by the one-shot 28 and setting the trigger 26 to one state sets the minimum non-random part of the polling pulse duration equal to 2Tp. Under this condition, the overlap of polling pulses transmitted by different subscribers of the network is always ensured.

Fully polling pulse

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a line having a random component of the total duration and defining a random subscriber priority value is generated at the output of the trigger 26

until the occurrence of a positive strobe pulse front from the output of the generator 29, which is closest to the instant of termination of the pulse at the output of the one-shot 28, i.e. the random component of the polling pulse duration is determined by the random phase relations between the moment of termination of the one-shot 28 pulse and the positive circuit of the next-nearest pulse generator 29.

Thus, in general, the duration of a polled pulse of a link state is a random value, taking any values in the range from the minimum limit determined by the pulse duration of the one-oscillator 28 to the maximum limit determined by the frequency generator 29 "

The key 31 of the transmitter (Lig. 6) is designed to control the generator in block 1 matching with the line that converts the signals from the output of the element OR 7 into current pulses transmitted to the communication line

The comparator 32 of the receiver 3 (FIG. 7) is designed to recover in amplitude and duration of a signal received from a line, generally weak and distorted,

In block 1 of matching with the line (FIG. 8), a controlled current generator 34 with high output resistance and a decoupling amplifier 35 with high input resistance, made, for example, according to the emitter follower circuit, High input-output unit 1, are used. connected to line 11, reduces the influence of the device's connection point on the electrical properties of the line and reduces signal distortion due to the heterogeneity of the communication line.

Signals to the inputs 12 and 14 of the device come from the registers of the transmitted data and commands of the interface equipment of the subscriber of the local network of the EVM.Signals from the outputs 1 3 and 15 of the device go to the registers of received data and commands of the above interface equipment with

The device works as follows.

In the initial state, the signal is a Transmission Request at the device input 14 is absent, while the output of the block

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8 is blocked and signals in the form of current pulses are not transmitted from the device to line 11. With the level O coming from the input 14, the block 4 is kept in the initial zero state „

The device starts to work after the arrival at input 14 of the signal Transmission request (in the form of 1) to the input of the And 9 element, the reset input of the block 8 and the input of the 4 block. And 9. The same signal unlocks the triggers 16 and 17 of the line condition analysis block 4

If at this time the signal 11 is transmitted by some other device from those connected to the communication line, then these signals from the output of unit 1 through receiver 3 arrive at the input of unit 6, which in this case detects a busy line condition, prohibiting Signal transmission Request transmission through element 9 s At this, the device waits for a signal in the form 1 to release the communication line from the output of block 60

If the line 11 is cleared before it is cleared, then block 6, detecting the absence of signals in it for a specified interval, generates a link state signal, which, if there is a signal, Transmission request and if there is no signal Enable transmission through AND 9 element as a request signal to the input unit 8 of the formation of the impulse polling line state. In addition, the signal about the free state of the communication line, entering the second input of the node, 10, blocks informational subscriber output 13.

The polling pulse through the element OR 7, the transmitter 2 and the matching unit 1 enters the line 11 for transmission to all similar devices connected to the line. In addition, through the block 1 and the receiver 3 the polling pulse returns to the device from where it was transmitted. From the output of the receiver 3, the polling pulse is fed to the input of the line state analysis unit 4. Simultaneously with the transmission in line 11 of the pulse-survey from the output of the transmitter 2, the line to the minute, is fed to the input of the block 5 time selection,

the time of selection of ST, 1 signal 1, on the free

where its rear (positive) front is delayed. Next, from the output of block 5, the impulse delayed by the back positive Lronth is received and sent to the input of block 4, where the value of the signal received from the line and received at the input of block 4 is thankful the edge delay, the fixation of the value of the signal JQ is performed only after the end of the polling pulse transmitted by this device.

Further operation of the device depends on the presence in the communication line of an impulse jc from another device at the moment of fixing the line state.

With a free line of communication, the device operates as follows.

Since in this case, at the moment of fixation, there are no polling pulses transmitted by other similar network devices, block 4 generates a signal to enable transmission in the form of level 1. This signal arrives at the inverse input of the And 9 element, blocking the ability to restart block 8, and also output to device 15, causing an arrival

Since the priority of the network subscriber is determined by the duration of the interrogation pulse ei randomly selected, depending on the ratio of the impulse / coupling durations involved in the collision, the response of each device to the collision is different.

If in the device the duration of the own interrogation pulse exceeds the duration of the foreign one, then in block 4, the unoccupied state of the communication line is fixed and the transmission permission signal is generated. At the same time, further operation of the device is similar to the operation of the device with a free communication line.

If in the device the duration of the own polling pulse is less than the duration of the alien, then the delayed positive and front 5 unit of the own polling pulse received at the third input of unit 4, fixing the presence of someone else’s received from the polling pulse line in the form of level A. In this case, in block 4, the signal Resolution

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transmissions are not normalized, and the device enters sig

on the information subscriber input of ed. 1 about the release of the communication line 12 transmitted modulated information signals. Through element 7, transmitter 2 and block 1, modulated information signals of output of block 6, Formula

the invention

1. A device for interfacing a subscriber with a communication line of a local network EVE, containing a matching unit with a line, the input-output of which is with the input-output of the device for connecting to the communication line of the local computer network, and the receiver input and the main output of the transmitter, the input of which is connected to the output of the OR element, the first input of which is the subscriber information input of the device, and the second input is connected to the output of the polling pulse generation unit connected to the start input To the output of the element I, the first input of which is the subscriber input of the device transfer request, characterized in that, in order to increase the reliability of the operation of the device, a communication line state analysis block is inserted into it, two time signal selection units and a node interlocking the subscriber output, and the additional output of the transmitter is squeezed into line 11. Signal The transfer request must be issued by the interface equipment of the subscriber of the local computer network during the entire transmission time deformations of because upon release of this signal proizvdits the initialization state of block 4 that stops transmission of a signal Lormi- resolution.

At the moment of termination of the polling pulse received from the line (formed by the data or any other similar device), the first input of the block 10 unlocks the information output of the subscriber 13.

When a collision of polling pulses in a communication line, the device operates as follows.

This situation may occur if, after the release of the previously occupied communication line, almost at the same time, the transmission of the interrogation pulse several times

jc

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Since the priority of the network subscriber is determined by the duration of the interrogation pulse ei randomly selected, depending on the ratio of the impulse / coupling durations involved in the collision, the response of each device to the collision is different.

If in the device the duration of the own interrogation pulse exceeds the duration of the foreign one, then in block 4, the unoccupied state of the communication line is fixed and the transmission permission signal is generated. In this case, the further operation of the device is similar to the operation of the device with a free line of communication.

If the device has a duration of its own polling pulse less than the duration of a stranger, then the delayed positive front of its own polling pulse delayed by block 5, arriving at the third input of block 4, records the presence of a foreign received from the polling pulse line in the form of level A. In this case, signal 4 Resolution

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transmission is not normalized, and the device goes into standby mode signal 1 about the release of the communication line

from the output of block 6, Formula

the invention

Nala 1 on the release of the communication line

Claims (4)

1. A device for interfacing a subscriber with a communication line of a local network EVE, containing a matching unit with a line, the input-output of which is the input-output of the device for connection to the communication line of the local computer network, and the output and input, respectively, to the input of the receiver and the main output of the transmitter, whose input is connected to the output of the OR element, the first input of which is the subscriber information input of the device, and the second input is connected to the output of the polling pulse generation unit connected to the start input And to the output of the element I, the first input of which is the subscriber input of the device transfer request, characterized in that, in order to increase the reliability of the device, a line state analysis block is entered into it, two time signal selection blocks and a blocking node a normal subscriber output; the additional output of the transmitter is connected to the clock input of the link state analysis unit through the first time-based signal selection block; connected to the first output of the receiver, and the reset input - to the subscriber input of the device transfer request and the reset input of the PULSE CONDITION PULSE FORMING unit; the second output of the receiver is connected to the second input of the AND element and the installation input of the blocking node subscriber output, the sync input of which is connected to the second output of the receiver, and the output is the subscriber information output of the device, the third input of the AND element is connected to the output of the link state analysis block and the output of the transmission enable of the device. 2. Device pop 1, characterized in that the link state analysis unit contains two triggers and two optocoupler nodes, the output of the first; the trigger is connected to the synchronous input of the second trigger, the information input of which is connected to the unit potential bus of the device, and reset input — with a reset input — the first trigger and through the first node of the optocoupler with the device reset input; the output of the second trigger is connected via the second node of the opto-isolator with the output of the unit, the synchronous input and the information input of the first trigger; are respectively synchronizing and information input unit, 3. The device according to claim 1, characterized in that the temporal signal selection block contains a constant voltage source connected to the integrator input, a threshold element whose output is the output of the block, and a key and the key input is input the block, the outputs of the key and the integrator are connected to the input of the threshold element. 4. Device According to 1, characterized in that the blocking information subscriber output contains a trigger, the installation input of which is the installation input of the node, and the OR element, the output and the first input of the OR element are connected respectively to the output of the node and the trigger output, information input connected to the bus of zero potential of the device, the second input of the OR element is connected to the synchronizing input of the node and the synchronous input of the trigger „ th From (MHuro 3 fxoi " (hi reception- j From K Y BwodfS LT # / wl r Aatja OnieoftS tul.l II ts Qm G Oha 7 0yZilo / 0ui 6 Ominono f K sstoxy Kfaoxy 4 Fi9 7 % line ft fin ntfH & JI  t  J t Fi $ ..HoHtMtn survey n / that isto itm Pui 9