SU1183977A1 - Interface for linking subscribers with communication channel - Google Patents

Description

The invention relates to computing, in particular to local (local) data networks between computers and intelligent complexes - technical means, 5

using a common trunk channel.

The purpose of the invention is to reduce the time of message delivery through the backbone communication line by reducing the access time to the communication channel during the dynamic distribution of message priorities.

FIG. 1 shows the device block diagram; in fig. 2 - structured pulse generator circuit; in fig. 3 is a diagram of a preamble collision analysis node; in fig. 4 is a diagram of the first counter; in fig. 5 - block diagram of the fixation of the presence of signals. 20

The device contains (Fig. 1) block 1 coordination with the channel, the transmitter 2, the receiver 3, the block 4 fixing the presence of the signal, the second element And 5, the main channel (line) 6, node 7 25

forming the preamble signal, the second element OR 8, the second counter 9. time, the node 10 analysis of the collision of the preamble, the first counter 11 time, the first element AND 12, the generator 13 pulses asynchronous, the first element ^: ment OR 14, information subscriber input 15, subscriber input 16 transfer request, triggering input 17, information subscriber output 18, setup input 19, input 20, prohibiting input 21.

An embodiment of the non-synchronous pulse generator 13 is shown in FIG. 2. It consists of the multivibrator 22, the binary counter 23 and the group element I 24. The period of the pulse of the multivibr2

torus is greater than 2c _p , where C _p is the propagation time of the signal in the communication channel, and is determined by the formula

,

where 2 is the length of the communication channel, km;

LP is the time constant of the signal propagation in the line, μs / km.

The pulses of the multivibrator 22 arrive at the clock input of the counter 23, and its current state coincides with the signal at the first control input 17 through the group element AND 24 enters. At the input of the element OR 14.

An embodiment of the preamble collision analysis node 10 is shown in FIG. 3. It consists of the element HE 25 and two elements AND 26 and 27.

The time counter 9 can be performed on the one-shot.

The implementation of the counter 11 is presented! in fig. 4. It consists of the element And 28, the binary counter 29, the decoder 30 filling the counter. In the initial state of the counter (reset circuit not shown) the output of the decoder 30 has a signal. When a code signal is received from an element OR 14, a binary number is written in parallel to counter 29, and the signal from the output of decoder 30 is removed. The counter 29 remains in this state until an enable signal arrives at the AND 28 from the analysis node 10. On the other

> input element And 28 receives pulses, the sequence of which> / 2c _p , for example, from the multivibrator 22. From element 28 to the counting input of the counter 29 impulses arrive before it is filled. Descrambler 30 after 3 1183977. four

Completion of the counter 29 prohibits through the AND 28 element the arrival of counting pulses to the counter input, blocking its operation, and the signal from the decoder output also goes to the ₅ And 12 element and to the first control output 21.

An embodiment of block 4 for signaling the presence of a signal is shown in FIG. 5. It consists of an element

31 by bit comparison and counter 32. Counter 32 is an integrator designed to distinguish random interference from collisions or a foreign transmission in a channel. Initial state counter

32 reset (reset circuit not shown) and there is no signal at its output. Element 31, representing the bitwise comparison scheme, when there is a zero signal from the element OR 8 compares it with the signal from receiver 3, and when a single signal from receiver 3 is detected, the signal from the output of element 31 goes to the counting input of the counter 32. The output signal of the block

4 fixing the presence of a signal appears when the counter overflows 32.

The signal at the output of block 4 appears in two cases: the proposed device does not transmit signals to. ^ 0

Trunk line 6, but at this time there are signals transmitted by another device (the channel is busy); the device began transmitting signals to the free trunk line 35, after which a signal is detected in the line that does not coincide with the transmitted one (collision).

A preamble is a code sequence that is transmitted to the communication channel for it. classes. This sequence also serves for bit-wise synchronization of the receivers with the transmitter. Kind of sequence determined Me- ¹⁵ Tod modulation signal in the communication channel. The number of preamble sequence elements depends on the priority of the message and the presence of a collision in the communication channel. '0

The preamble can be a sequence of the form 101010101010 101 ..., the node 7 of the formation of such a sequence can be performed on a single-bit counter. 55 Block 1 matching is a transformer with matched input and output impedances. "

The device controls the access of messages to trunk channel 6 depending on their priority, "sending a preamble signal to the channel and analyzing the presence of a collision.

Trunk channel 6 is a double-ground communication channel several kilometers long, to which a number of devices similar to the one proposed are connected according to the multipoint scheme.

The unit 4 fixing the presence of the signal controls the presence of a carrier in the communication channel, compares the signals arriving at the input of the transmitter 2 with the signals received from the line through the receiver 3.

The signals 15, 16, 17 and 19 are fed to the inputs of the device from the command registers and the transmitted data of the interface equipment of the subscriber's local network, for example, a computer. The signals 18, 20 and 21 from the outputs of the device are sent to the status registers and the transmitted data of the named interface equipment.

Node 10 collision analysis of the preamble in the absence of a signal at the input from the element And 12 at the outputs does not issue signals.

In the presence of a signal from the element And 12 and the absence of a signal from block 4 at the second output of the node 10 analysis there is a signal - the absence of a collision of the preamble. ·

In the presence of signals from element 12 and block 4, there is no signal at the second output and there is a signal at the first output of the analysis node 10 — the presence of a preamble collision with any signal in the communication channel.

The time counter 9, in the presence of a signal at its input, counts the time required for reliable detection of a preamble collision in the communication channel, more than 2Cp.

Counter 11 determines the transmission time of the preamble to the communication channel. It. the time is greater, the higher the priority of the message, and is determined by the state of the counter, in which it is given by the installation input by a signal from the element OR 14. In the simplest case, a number is entered with this signal, and the signal at the output of the counter 11 appears after it is filled.

five

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Clock circuit counters 9 and 11 are not shown.

The device works as follows.

In the initial state, the counter 9 is reset and does not issue a signal at the output, and the counter 11 is full and outputs a signal at the output.

The device begins to work after the receipt of the "Request Transmission" signal at input 16 at the first input of the And 12 element. At the same time, via installation input 19, OR 14 and the installation input, time counter 11 is set to the state that determines the priority level of the message requesting the transfer. The signal from the output of the counter 11 is removed.

Further operation of the device depends on the presence of the preamble signal from another device in the communication channel and on the priority level set in the counter 11.

Operation of the device with a free channel.

In this case, there is no signal at the output of block 4, therefore, at the output of element 5 there is also no signal. After setting the priority level in the counter 11, there will also be no signal at its output, therefore a signal "Transmission Request" at the output of the And 12 element gives a signal allowing the operation of the preamble signaling node 7. The preamble signal through the element OR 8, the transmitter 2 and the matching unit 1 enters the main channel 6. From the output of the element AND 12 to the first input of the analysis node 10 receives a signal on the transmission of the preamble. Since there is no signal at the second input of the analysis node 10, the second output will be a signal from which counter 9 will start. If during the time the counter 9 was in operation, the preamble did not collide in the channel, the output of the counter 9 shows the signal "Information transmission resolution, which goes to the input 20 and the third input of the element And 12. The signal from the output of the And 12 is removed, and the transmission of the preamble from the node formation 7 stops. On the signal "Enable transmission of information" to the information input 15 begins to receive "Transmitted information", which t OR 8 transmitter 2

and block 1 will be transmitted to the communication channel. The “transfer request” on entry 16 at this time must be cleared.

The operation of the device when a "Transmission Request" appears on input 16 with a busy communication channel.

In this case, from the output of block 4 to the second input of element And 5, the signal of coincidence with the missing signal from element 12 will come. The signal from output of And 5 prohibits on the fourth input element And 12 until the communication channel is released and the signal at the output of block 4 will disappear. After that, the device will operate as with a free channel.

The operation of the device in the collision of the preamble in the communication channel.

The mode may arise, for example, in the case when, after the release of an occupied communication channel, almost simultaneously several devices began to transmit to the preamble channel.

In this case, block 4 detects a collision and sends a signal to the second input of the analysis node 10, at the first input of which there is already a signal from the And 12 element about the preamble transmission. From the second output of node 10, the signal is removed and the counter 9 is reset. At the same time, the signal from the first output of the analysis node 10 is started at the second input of counter 11.

Further operation of the device depends on the ratio of priority levels, messages, whose preambles are encountered in the communication channel.

The device continues to transmit the preamble with continued interruption until the counter 11 is full.

The signal from the output of the counter 11 prohibits the element 12 from the second input and stops transmitting the preamble. The same signal from the counter 11 through the input 21 reports a conflict situation.

This situation occurs when a preamble of a higher priority message is encountered.

If, before filling the counter 1 1, block 4 detects the disappearance of a preamble collision in the channel, the signal from its output disappears, and the analysis node 10 removes the signal from the first output and stops the operation of counter 11.

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At the second output of the analysis node 10, a signal appears that triggers the counter 9. After the counter 9 has been processed, the signal from its output goes to input 20, allowing information to be transmitted, and also prohibits the And 12 element on the third input. prohibits the operation of the preamble signal generation node 7 and its transmission to the communication channel. By information entry

15 starts a message that through the element OR 8, the transmitter 2 nd unit 1 will be sent to the Trunk channel 6. Signal "Transmission request" on the control input

16 during the transfer of the message must be removed.

In the event that an informational message was not transmitted due to a conflict situation that was reported at input 21, an attempt to retransmit may be attempted. To do this, with the new "Request for Transmission" to the counter 11 through the element OR 14 through the installation input 19 you can enter another level

priority, or at input 17 from the generator 13 pulses of non-synchronous to enter the current state of the ring counter of the generator, which 5 will determine the random priority level of the message.

In the proposed device, in comparison with the known, the access time to communication channel 0 is reduced due to the fact that when a request for transmission appears, the device transmits a code sequence - a preamble, the number of elements of which depends on the message priority and the presence of a conflict situation in the collision channel simultaneously channel messages.

If there is a “pause” in the trunk line, the device provides access to the communication channel with almost no delay, regardless of the message’s priority. Priority plays a role only in the resolution.

25 conflict situations - collisions in a communication channel simultaneously messages that have entered the channel.

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Claims (1)

A DEVICE FOR CONNECTING SUBSCRIBERS WITH A COMMUNICATION CHANNEL, containing a channel matching unit, a transmitter, a receiver, a signal presence latching unit, the input / output of the channel matching unit is the device information input / output, the receiver output is connected to the first input of the signal presence latching unit and is an information subscriber output of the device, the second input of the block for fixing the presence of a signal is connected to the input of the transmitter, the output of which is connected to the input of the matching unit with a channel, characterized in that, in order to reduce the delivery time of a message over a communication channel by reducing the access time to a communication channel when dynamically distributing message priorities, a preamble signaling node is entered into it, for example, as a counter, analysis node collisions of the preamble, pulse generator, two counters, two elements OR, two elements AND, the trigger input of the pulse generator is the trigger input of the device, the first input of the first element OR is the installation input of the device, the first input of the second element OR is the information subscriber input of the device, the first input The first element And is the subscriber input of the device transfer request; the outputs of the first and second counters are connected to the second and third inputs of the first § of the And element, respectively, and are forbidding and permitting outputs of the device, the output of the first element I is connected to the first input of the preamble collision analysis node, to the first input of the second element AND and to the input of the preamble signal conditioning node, the output of which is connected to the second input of the second OR element, whose output is connected to the second input block fixing the presence of a signal. the output of which is connected to the second inputs of the collision analysis unit of the preamble and the second element AND, the output of which is connected to the fourth input of the first element AND, the output of the pulse generator is connected to the second input of the first element OR, the output of which is connected to the installation input of the first counter, the enabling input of which is connected to the first output of the collision analysis section of the preamble, the second output of which is connected to the permissive input of the second counter, while the analysis node is table 811. „1183977 1183977 the preamble’s clause contains two AND elements and a NOT element, the first input of the first element AND connected to the first input of the second element AND and the first input of the collision analysis node of the preamble, the second input of the first element AND connected to the input of the element NO and the second the preamble collision analysis node input, the outputs of the first and second elements AND are the first and second outputs of the preamble collision analysis node respectively, the output of the element is NOT connected to the second input of the second element I. one