JPS5941941A - Signal transmitting circuit - Google Patents

Abstract

PURPOSE:To reduce the load factor of a communication line, by switching the circuit state between the time of the start of data transmission from a station and the time, when the station receives data transmitted round on the communication line after completion of transmission, to prevent the transmission of frames transmitted round on the communication line. CONSTITUTION:When a station A is the transmission right control station and a station C is the data frame transmitting station, the station A is switched from a repeat mode MR to a transmission mode MT at a time t1 to transmit a transmission right frame TN and a GA pattern and is set to the transmission completion state, and a switching register is reset at a time t7 when the station A receives an end flag 57 of the frame TN transmitted round on the communication line, and the station A is switched to the mode MR again. Thus, frames fllowing the frame TN which is transmitted round on the communication line are transmitted, and the remainder of this frame TN is not transmitted onto the communication line.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a signal transmission circuit, and particularly to a signal transmission circuit suitable for nHm communication in a loop-shaped communication path.

In data communication networks, multiple stations are connected using multidrop, loop, star, etc.
A loop shape is suitable from the viewpoint of high speed response and high throughput. Furthermore, nHm communication, which enables communication between any station and any other station, is expected to be widely adopted in the future.

In order to realize n;m communication, unlike in the case of lHn communication, it is necessary that the data on the communication path goes around the communication path only once and does not exist on the communication path beyond the - round. Since this is difficult, this has been one of the reasons for hindering the spread of n:m communication.

FIG. 1 is a schematic diagram of loop communication. In FIG. 1, five stations A-E are connected to a loop-shaped communication path 51. In FIG. The direction of data transmitted through the communication channel 51 is
For example, as indicated by the illustrated arrow. ! In addition, each station has its transmitting end and receiving end connected to a communication path 51.

Each station A to E is composed of a signal transmission circuit that performs serial-parallel conversion of transmitted and received data and frame control, a memory that stores data, an interface section with the application side, and a command section that controls these. It goes without saying that the command section may be constructed of either random logic or a microcomputer. Note that the signal transmission circuits of stations A to E are all composed of the same circuit.

In n:m communication, each station A-E uses a communication path 51 from the upstream station.
There is a need for a repeat mode in which the data received via the station is sent as is to the downstream station, and a transmission mode in which each station A to E itself sends data to other stations, and these two modes can be switched as necessary. ing.

Further, each station A to E can transmit data to the communication path 51 at the time when it receives a transmission right signal indicating the transmission right and confirms that there is no frame following the transmission right signal. Only one transmission right signal exists on the communication path 51.

FIG. 2 shows an example of the structure of serial data to be transmitted.

The serial data shown in FIG. 2 is l(igh I, evel
Data, ink (hereinafter abbreviated as HDLC).

) according to the procedure. The delimiter of a frame, which is a collection of data, is indicated by a start flag 52 and an end flag 57, and the bit patterns of both flags 52 and 57 are the same and are fixed as "01111110". Following the start flag 52, there is a destination address 53 indicating the station number to be received.
A control unit 54 that controls the communication link status between two stations
, an FCS that performs error checking between the information section 55, the destination address 53, the control section 54, and the information section 55.
(Frame Check 5eque-nce)5
6, and finally a termination flag 57.

There are various transmission right signals, following tt o #l < tt
When seven consecutive 1n's (hereinafter referred to as GA pattern) are received, the seventh "1" is changed to °'0" and this is used as a start flag.
There is a method of combining GA butter/. The former GA
In the pattern-only method, if the idle data between frames is 1'', it may turn on due to noise.
Use pattern A.

The transmission right management station that generates and transmits the transmission right signal is fixed to one station in advance so that only one station exists at the same time on the communication path 51, or is it alternated in a sequential manner. Alternatively, it may be decided each time by a method such as determining one station from among all stations A to E.

Next, a conventional signal transmission circuit and the flow of transmitted frames will be explained using FIGS. 3 and 4.

FIG. 3 is a block diagram of a conventional signal transmission circuit, and FIG. 4 is a frame flow diagram in the case of FIG. In FIG. 3, received data r (D is a serial/parallel conversion circuit 2 that converts serial data into parallel data) received from a communication path 51 which is a DC data string, and a GA detection circuit 3 that detects an OA pattern of a transmission right signal. , the flag detection circuit 4 that detects the start flag 52 or the end flag 57, and the first selection circuit 14 that selects data to be transmitted to the communication channel 51 in the repeat mode.

The data converted into parallel data by the serial/parallel conversion circuit 2 is
After being temporarily stored in the reception buffer register 5, it is transferred to a memory (not shown) via the parallel data bus 20.

On the other hand, the fact that the OA pattern has been detected by the OA detection circuit 3 is stored in the status register 6, and the status register 6 outputs a transmission start permission signal 22 to the transmission control circuit 9. The flag detection circuit 4 still detects the start flag 52 or the end flag 57.
is detected and stored in the status register 6. This indicates that frame transmission has started or ended. The contents of the status register 6 are reported to a command unit (not shown) via the parallel data bus 20 as necessary.

Information for controlling the transmission and reception of data from the command section is stored in the control register 7. The data to be transmitted to the communication path 51 is still stored in the transmission buffer register 8 from the memory as needed. The transmission data stored in the transmission buffer register 8 is converted from parallel data to serial data by the parallel/serial conversion circuit 10, and FC856 is generated by the PCS generation circuit 11. In addition, the GA pattern is a GA generation circuit 12,
The start flag 52 and the end flag 57 are generated by the flag generation circuit 13.

The transmission data TD sent to the communication path 51 in the repeat mode or the transmission mode is selected by the first selection circuit 14 as the reception data RD or from the serial/parallel conversion port QIO, the PCS generation circuit 11, the flag generation circuit 12, and the GA generation circuit 13. One of the outputs of the second selection circuit 15 that selects one of the outputs is selected. Note that the first selection circuit 1
4 and the second selection circuit 15, respectively;
The repeat switching signal 26 and the transmission switching signal 27 are generated by the transmission control circuit 9.

The transmission/repeat switching signal 26, the transmission switching signal 27, the parallel/serial conversion circuit 10, the FC8 generation circuit 11, the flag generation circuit 12, and the signal that controls the GA generation circuit 13 are generated by the transmission control circuit 9. , control register 7
It operates according to the transmission request signal 23, the repeat signal 24, and the transmission start permission signal 22 from the status register 6.

Reception data RD and transmission data TD are transmitted and received in synchronization with clock CLK from a separately provided clock generation circuit. Since there is a repeat mode in loop communication, the reception clock and the transmission clock need to be in the same phase, and can be a common clock CLK.

Next, the flow of frames will be explained with reference to FIG. Assume that station C is the station requesting transmission data from station A1, which is the trust management station. Further, it is assumed that '1' is transmitted between frames in which no data is transmitted.

Station A switches from repeat mode to transmission mode at time 11, transmits a transmission right frame TN and a GA pattern, and thereafter transmits idle data "1". Station B~
Station E is in repeat mode, but when station C receives the transmission right signal it switches to transmit mode and prepares to transmit frame FC.

The data to be transmitted has a time delay that is the sum of the time delay caused by the communication path 51 and the time delay caused by the repeat mode and driver receiver circuit of each station. This has been corrected so that all stations A to E can transmit and receive correctly.

Station B transmits the received data to station C in repeat mode. Station C is waiting to receive a transmission right frame TN since there is a transmission request. When the start flag 52 of the transmission right frame TN is received, the flag detection circuit 4 stores the fact that the start flag 52 has been detected in the status register 6,
Report to the command center. The command part is receive buffer register 5
The data received via the parallel data bus 20 is captured and decoded, and the received frame becomes the transmission right frame TN.
If it is determined that the pattern is the same as that of
When the detection circuit 3 detects the GA pattern, it switches to the transmission mode and transmits the frame FC, so the repeat signal 24 of the control register 7 is reset. Accordingly, when the station C detects the GA pattern with the GA detection circuit 3, it outputs the transmission start permission signal 22, and at time tz, the transmission/repeat switching signal 26 converts the selection signal of the first selection circuit 14 into the received data It, Second selection circuit 1 that becomes transmission data from D
Switch to output 5.

Since station E is in repeat mode, the received data from the communication path 51 of the upstream station is directly transmitted to the communication path 5 of the downstream station.
Send to 1. The station that matches the contents of the destination address 53 in the frame detected by station C transfers the frame FC to the command unit.

After being transmitted from station A, the transmission right frame TN goes around the communication path 51 and returns to station A again. - The circulated transmission right frame TN is no longer needed in n:m communication, so
It is deleted by the station A that sent it.

The first method for erasing is that after the command section recognizes that the transmitted transmission right frame TN has been received, the command section immediately requests the repeat signal 24 to enter the repeat mode, and at time t3, the command section There is a method of switching the selection circuit 14 using the transmission/repeat switching signal 26 to set station A to the repeat mode.

The second method is to report to the command unit that the termination flag 57 of the passed transmission right frame TN has been received.
There is a method in which the command unit requests the repeat signal 24 to enter the repeat mode and sets the station A to the repeat mode.

Here, according to the first method, a part of the transmission right frame TN is erased, but a part is not in the repeat mode.
The remaining transmission right frame remains as TR and is transmitted to the downstream station. On the other hand, according to the second method, if the transmission data continues after the transmission right frame TN, the beginning of the transmission data will be erased due to the processing delay from frame detection in the command unit to the repeat mode instruction. It will be done.

FIG. 4 shows the case of the first method, in which the transmission mode MT is from time t1 to time t3, and time t
3 and onwards are repeat modes Mu.

Similarly, when station C transmits an incoming transmission frame FC and returns to it after going around the communication path 51, station C receives a transmission frame F.
Delete C. This erasure method includes the first and second methods, similar to the erasure of the transmission right frame TN at station A described above. FIG. 4 shows the case of the first method, in which a portion of the transmission frame pc is sent out to the communication channel 51 as the remaining transmission frame FR. At station C, time t2
The transmission mode MT is from to time t4, and the repeat mode MR is from time T4.

As mentioned above, 1. In both of the second methods, it is not clear how to distinguish between frames that should be erased and frames that should be repeated and sent to a downstream station, and has the following drawbacks. In other words, due to the endless circulation of the transmission right frame remaining TR, transmission frame remaining, and DFR, which are unnecessary data, on the communication path 51, the flag detection circuit 4 of each station A to E is activated, and the processing at the command unit increases. It becomes a visitor to the original processing operations of the command center. The load factor of the communication path 51 still increases. The load factor on the command center due to unnecessary data patrols is 1 for each Rougou tour.
Processing with two remaining frames continues indefinitely.

As is clear from the above description, the conventional technology has the drawback that the load factor of the command unit is high and the load factor of the communication channel 51 is high, making it impossible to transmit correct frames.

The present invention has been made in view of the above, and its purpose is to transmit signals that can reduce the load factor of the command unit and the communication path, and that can correctly circulate the transmitted data through the communication path. The purpose is to provide circuits.

A feature of the present invention is that each station connected to the loop communication path has a transmission mode in which it transmits data and a repeat mode in which it transmits data received from an upstream station to a downstream station. A switching register that sets either one, a selection circuit that selects data received from the upstream station or data sent from the own station depending on the state of this switching register, and a frame detection that detects that one frame of data has been received. a first AND circuit that manually generates a transmission completion signal indicating the completion of transmission from the own station and a frame detection signal that is the output of the frame detection circuit; A second OR circuit inputs a requested repeat signal manually, a transmission request signal requesting transmission from its own station, and a transmission start permission signal based on a transmission right signal indicating a transmission right received from the upstream station. and a transmission control circuit configured with an AND circuit, wherein the switching register is brought into a first state by the output of the first AND circuit and selects the repeat mode;
On the other hand, when the transmission mode is selected by being held in the second state by the output of the second AND circuit, and the own station starts transmitting data, the switching register is switched to the second state; When receiving the data that has gone around the communication path after the end of own station transmission, the switching register is switched to the first state, and the data ends after just going around the communication path.

The embodiment of the present invention shown in FIG. 5 and FIGS. 6 and 7 will be described below.
This will be explained in detail using figures.

FIG. 5 is a block diagram showing an embodiment of the signal transmission circuit of the present invention. The same parts as in FIG. 3 are designated by the same reference numerals, and the explanation thereof will be omitted here. In FIG. 5, the transmission control circuit 9'
is composed of a frame detection circuit 30, a first AND circuit 31, an OR circuit 32, a switching register 33, a second AND circuit 34, and a transmission end generation circuit 35. When the own station is in transmission mode, it transmits a frame. One frame is received by the frame detection circuit 30, which receives the transmission completion signal 21 generated by the transmission completion generation circuit 35 indicating that the transmission has been completed, and the outputs of the flag detection circuit 4 and reception buffer register 5, and generates a termination flag. The switching register is activated by the output of the AND circuit 31 which receives as input the frame detection signal 36 from the frame detection circuit 30 indicating that 57 has been received, and the output of the OR circuit 32 which receives as input the repeat signal 24 from the control register 7. 33 to the reset] state, the switching register 33 generates the transmission/repeat switching signal 26 for the first selection circuit 14, and returns.

FIG. 6 shows the flow of frames in FIG. 5 when station A (see FIG. 1) is a transmission right management station and station C is a data frame transmitting station. 8A switches from the repeat mode MR to the transmission mode MT at time tl, transmits the transmission right frame TN and the GA pattern, is set to the transmission completion state, and finishes receiving the termination flag 57 of the transmitted transmission right frame TN. Then, at time t7, switching register 3
3 becomes a reset state and is switched to repeat mode MR again. As a result, the transmitted right frame T
The frame following N can be transmitted from the upstream station to the downstream station, and the remainder of the passed transmission right frame TN will not be transmitted on the communication path 51 (see FIG. 1).

Here, the time t when station A switches to repeat mode MR
7 is after station A finishes transmitting the GA pattern, and transmission completion is set at the end of transmitting the GA pattern. Therefore, the time t7 at which the mode is switched is when station A finishes transmitting the GA pattern or when the end flag 57 (see FIG. 2) of the completed frame is received, whichever is later.

Station C receives the transmission right frame TN and the GA pattern, is switched from repeat mode MR to transmission mode MtK at time t2, and transmits frame FC. After the frame FC has made one round on the communication path 51, the station C terminates the frame FC 7.
When lag 57 is received, the transmission mode MT is set at time t7.
The mode is switched from MR to repeat mode.

The state of the transmission/repeat switching signal 26 which is the output of the switching register 33 in this case is shown for each station A to E in FIG.

According to the embodiment of the present invention described above, as is clear from the above description, a part of the frame after the cycle remains on the communication path 51 and is not transmitted.

Therefore, the load factors of the command unit and the communication path 51 can be reduced by about 10%.

Although the frame used in the description of the above embodiment has the configuration shown in FIG. 2, the effect will not change even if frames with other configurations are used. In this case, the start flag 52
If the pattern of the termination flag 57 is different, the GA pattern must also be different, so it is necessary to change the GA generation circuit 13, GA detection circuit 3, flag generation circuit 12, and flag detection circuit 4 to correspond to the pattern. Needless to say.

However, a delay circuit that delays the transmission time of the OA pattern may be provided in the reception section of the transmission right management station. In this case, the transmission right frame TN circulates through the communication path 51'i,
Since the time at which the frame returns to the transmission right management station is after the GA pattern is transmitted, it is immediately switched to the repeat mode MR at the time when the end flag 57 of the cycled frame is received.
The effect does not change.

As explained above, according to the present invention, since it is possible to prevent unnecessary data from being generated, it is possible to reduce the load factor of the command unit and the communication path, and also to prevent transmission data from disappearing and correct transmission data. This has the effect of making it possible to transmit the information to each station through one round of communication channels.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of loop communication, FIG. 2 is a block diagram of a conventional transmission signal circuit, FIG. 4 is a frame flow diagram in the case of FIG. 3, and FIG. 5 is a diagram of the transmission signal circuit of the present invention. FIG. 6 is a block diagram showing one embodiment. FIG. 6 is a frame flow chart corresponding to FIG. 4 in the case of FIG. 5. FIG. It is a diagram showing each round. 9'... Transmission control circuit, 14... Selection circuit, 21.
... Transmission completion signal, 22 ... Transmission start permission signal, 23
... Transmission request signal, 24... Repeat signal, 26.
... Transmission/repeat signal, 30... Frame detection circuit, 31... First AND circuit, 32... OR circuit,
33...Switching register, 34...Second AND circuit, 35...Transmission end generation circuit, 36...Frame detection signal, 51...(1 other person) Diagram 3 CLg → 13 Funeral diagram 5 procedural amendment (method) Director of the Japan Patent Office Kazuo Wakasugi 2. Title of the invention Signal transmission circuit 3. Relationship with the person making the amendment Patent applicant address (100) Tokyo Marunouchi-5-1, Chiyoda-ku, Miyako
Name (510) Hitachi, Ltd. Representative: Katsushige Mita 4, Agent Address (317) 3-10-chome, Kashima-cho, Hitachi City, Ibaraki Prefecture
No. Ibaraso Building 5, Date of amendment order: November 30, 1982 (shipment date) 6, Brief description of drawings in the specification subject to amendment 7, Contents of amendment

Claims (1)

[Claims] 1. In a serial data signal transmission circuit in which a plurality of stations perform n:m communication via a loop-shaped communication path, each station has a transmission mode for transmitting the data and a transmission mode for transmitting data from an upstream station. a repeat mode for transmitting the data to the downstream station, a switching register for setting either the transmission mode or the repeat mode, and depending on the state of the switching register, either the data received from the upstream station or the data transmitted from the own station is transmitted. a selection circuit that selects transmission data; a frame detection circuit that detects that one frame of data has been received; a transmission completion signal that indicates the completion of transmission from the own station; and a frame detection signal that is the output of the frame detection circuit. a first AND circuit as an input;
an OR circuit which inputs the output of the AND circuit and the repeat signal requesting the repeat mode, a transmission request signal requesting transmission from the own station, and a transmission right signal indicating the transmission right received from the upstream station to start transmission. and a second AND circuit that receives a permission signal as input, and the switching register is set to a first state by the output of the first AND circuit and selects the repeat mode. On the other hand, when the output of the second AND circuit is held in the second state and the transmission mode is selected, and the own station starts transmitting data, the switching register is switched to the second state. and when receiving the data that has gone around the communication path after the end of the own station transmission, the switching register is switched to the first state, and the data ends after just going around the communication path. A signal transmission circuit featuring: 2. The switching register is configured to be prohibited from entering the second state when it detects reception of a transmission frame from another station following the transmission right signal.
Signal transmission circuit described in section. 3. The signal transmission circuit according to claim 1 or 2, wherein the transmission right signal is managed by a transmission right management station arbitrarily selected and set from among the stations.