JPH0313778B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a data transmission system in which data is transmitted by branching connections between a trunk line and a plurality of terminal devices, and in particular, the present invention relates to a data transmission system that performs data transmission by branching connections between a trunk line and a plurality of terminal devices. The present invention relates to a branch control device in a data transmission system that allows data to be transmitted at seemingly the same time.

Conventionally, in data transmission systems for transmitting facsimile signals, etc., data is framed using, for example, high-level data link control procedures (HDLC) and sent from a switching center to a branch control device via a trunk line, and then this branch control is performed. Branching at a device and transmitting to a desired terminal device among multiple terminal devices,
Alternatively, there are devices that transmit data through the opposite route.

However, in the conventional branch control method between the trunk line and each terminal device in this type of system, the connection is established by operating a cross-point switch in the branch control device. Therefore, once a terminal device and a trunk line are connected, even if you make a call from another terminal device or try to transmit data to these terminal devices, the connected terminal device Data transmission could not be performed until the data transmission operation was completed.

The present invention has been made focusing on the above circumstances,
The purpose of this is that even if data is being transmitted between a trunk line and any terminal device, the connection between another terminal device and the trunk line can be made at any time without waiting for the end of this data transmission. It is an object of the present invention to provide a branching control device in a data transmission system that can transmit data between terminals and can perform efficient data transmission according to the number of terminals in a data sending state.

Accordingly, the present invention provides a data transmission system in which a branch control device performs branch connection between a trunk line and a plurality of terminal devices, and performs data transmission in frame units. The terminal-side circuit is connected to each corresponding terminal device, receives data frame by frame from the terminal device by supplying a transmission permission signal to the terminal device, and receives data of one frame. is temporarily stored in a storable first memory and then sent to the trunk line side circuit, and at the same time, when the trunk line side circuit completes reception of the one frame of data, the transmission permission signal is supplied to the terminal device. The relay line side circuit is connected to each of the terminal side circuits and the relay line, and is connected to one of the plurality of terminal side circuits.
In the order in which the terminal side circuits have completed receiving frame data, one frame of data is received from each terminal side circuit, and the received frame unit data is
The present invention constitutes a branching control device in a data transmission system characterized in that data of one frame is temporarily stored in a storable second memory and then transmitted to a trunk line in a time-division manner.

In this way, in the present invention, the data transmission period from the terminal device is set by sending a transmission permission signal from the branch control device to the terminal device, and when a plurality of terminal devices are connected to the branch control device, these By alternately sending out the above-mentioned transmission permission signals to the terminal devices to set the data transmission period from each terminal device, and thereby time-division multiplexing each data in units of frames and sending it to the trunk line,
Achieve the above objectives.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block configuration diagram of the branch connection device in the same embodiment, in which the control device connects a trunk line side circuit 2 connected to a trunk line 1 as a common line, and terminal lines 3, 4, and 5 (not shown). It is composed of terminal side circuits 6, 7, and 8 connected to each terminal device, respectively. By transmitting and receiving the output strobe signals ST1, -, ST6 and their response signals AS1, -, AS6 between the trunk line side circuit 2 and each terminal side circuit 6, 7, 8, the data base is It transmits and receives band signals BD1 to BD6. In addition, MD1, MD2, D in the figure
1,~,D6 contains the framed data and
ESA, ESB and ESC are connected to each terminal side circuit 6, 7,
8 to the terminal device.

Now, each terminal side circuit 6, 7, 8 is constructed as shown in FIG. Here, since the terminal side circuits 6, 7, and 8 have the same configuration, only the terminal side circuit 6 will be explained, and the explanation of the other circuits 7, 8 will be omitted.

That is, the terminal side circuit 6 includes a modulation circuit 61 that sends data D1 and a transmission permission signal ESA to the terminal device, a demodulation circuit 62 that receives and demodulates data D2 from the terminal device, a reception control circuit 63, and a transmission control circuit. 64 and each of these circuits 61,
. The demodulation circuit 62 demodulates data D2 from the terminal device and converts it into a baseband signal, extracts a clock signal from this signal, and temporarily stores the baseband signal using this clock signal. Then, this stored baseband signal is read out bit-parallel by a clock signal from the transmission control circuit 65 and guided to the transmission control circuit 65. Further, when data D2 from the terminal device is received by the demodulation circuit 61 and the transmission control circuit 65, the reception control circuit 63 transmits and receives an output strobe signal ST2 and its response signal AS2 to and from the trunk line side circuit 2. Then, baseband signal BD2 of data D2 is sent out.
On the other hand, the transmission control circuit 64 outputs an output strobe signal ST1 and a response signal AS1 between it and the trunk line side circuit 2.
After receiving and transmitting data, the baseband signal BD1 of data from the trunk circuit 2 is input.

FIG. 3 shows the reception and transmission control circuits 63,
64 and a transmission control circuit 65. FIG.
In the figure, the baseband signal BD2 output from the demodulation circuit 62 is transmitted to the HDLC controller 66.
The data is temporarily stored in the first memory (RAMIN) 67 through the process. After the output strobe signal ST2 is sent out and the response signal AS2 is detected by the CPU 68, it is sent out via the input/output port 69. On the other hand, the baseband signal BD1 from the trunk line side circuit 2 receives the output strobe signal ST1 and the response signal AS1 thereto.
After being sent out, the data is taken in through the input/output port 69 and stored in the second memory (RAMOUT) 70. After being read out by the CPU 68, it is outputted to the modulation circuit 61 along with a clock signal via the HDLC controller 66. The transmission control procedure for each of the above signals is as follows:
This is carried out according to a program preset in the program memory (ROM) 71.

On the other hand, the trunk line side circuit 2 includes a modulation circuit 21 that sends data MD1 to the trunk line 1, as shown in FIG.
, a demodulation circuit 22 that receives and demodulates the data MD2 from the trunk line 1, a transmission control circuit 23, a multiplex control circuit 24, a separation reception control circuit 25, and a transmission circuit that controls each of the above circuits 21, 25. It is composed of a control circuit 26. Separate reception control circuit 2
5 identifies the address information included in the data, that is, the destination information for each terminal device, when the data MD2 is taken in by the demodulation circuit 22 and the transmission control circuit 26, and identifies the corresponding terminal side circuit 6,
Baseband signal of the above data MD2 to 7 and 8
This is to distribute BD1, BD3, and BD5. Note that the baseband signals BD1 and BD1 of the data MD2 are
The sending operation of BD3 and BD5 is performed by sending output strobe signals ST1, ST3, ST5 between each terminal side circuit 6.
It is executed after sending and receiving response signals AS1, AS3, and AS5. On the other hand, multiplex control circuit 24
is to time-division multiplex the baseband signals BD2, BD4, BD6 sent from each terminal-side circuit 6, 7, 8, and the multiplexing operation is performed using the output from each terminal-side circuit 6, 7, 8. Strobe signal ST2, ST
4. Response signals AS2, AS4, AS6 to ST6
This is done by appropriately varying the return timing. For example, if the output strobe signal is ST2,
If ST4 and ST6 arrive in that order, each
A response signal is returned in the order of AS2, AS4, and AS6,
and the return timing for each baseband signal.
Set the time when BD2, BD4, and BD6 begin to be sent to trunk line 1 as data. i.e. response signal
AS2, AS4, and AS6 are generated every time data D2, D4, and D6 from each terminal device is sent to trunk line 1 for each frame.

FIG. 5 is a block diagram of the multiplex control circuit 24, in which 27 is a CPU and 28 is an input/output port. In the figure, each terminal side circuit 6, 7,
Output strobe signal ST2, ST output from 8
4, ST6 is detected by the CPU 27 via the input/output port 28. On the other hand, response signals AS2, AS4, and AS6 output to each terminal side circuit 6, 7, and 8 are
7 command causes the first memory (RAMOUT) 29
is read out from the input/output port 28 and outputted via the input/output port 28. Moreover, each baseband signal BD2, BD4, BD6 sent from each terminal control circuit 6, 7, 8 is
It is introduced through the input/output port 28 and temporarily stored in the second memory (RAMIN) 30. and CPU
After the output strobe signal ST7 and the response signal AS7 are exchanged between the output strobe signal ST7 and the transmission control circuit 23, the output strobe signal ST7 and the response signal AS7 are read out from the second memory 30 according to instructions from the CPU 27, and sent to the transmission control circuit 23 from the input/output port 28. It is now being sent to The transmission control of each of the above signals is entirely performed by the CPU 27 according to a program stored in a program memory (ROM) 31. Further, the memory 32 is for temporarily storing the baseband signals BD2, BD4, and BD6, and is constituted by a RAM.

FIG. 6 shows the transmission control circuit 23 of the trunk line side circuit 2,
It shows the configuration of a separation reception control circuit 25 and a transmission control circuit 26. In the figure, the baseband signal BD7 from the demodulation circuit 22 is introduced via the HDLC controller 33 and is temporarily stored in the first memory (RAMIN) 34. Then, this stored baseband signal BD7 is sent to the CPU 3.
5 identifies the address information, and CPU3
5 and each terminal side circuit 6, 7, 8, output strobe signals ST1, ST3, ST5 and response signal AS
1. After AS3 and AS5 are sent and received, the CPU
35, the signal is sent from the input/output port 36 to each terminal side circuit 6, 7, 8. On the other hand, the baseband signals BD2, BD4,
BD6 is introduced through the input/output port 36 and temporarily stored in the second memory (RAMOUT) 37.
Thereafter, the signal is sent to the modulation circuit 21 via the HDLC controller 33 along with a clock signal according to a command from the CPU 35. Note that 38 is a program memory for storing a control program for the CPU 35.

Next, the operation of the branch control device configured as described above will be explained with reference to timing charts shown in FIGS. 7 to 11. First, when data D2, D4, and D6 are sent from each terminal device A, B, and C to trunk line 1, the process is as follows.

For example, data (first frame) D is sent from terminal device A while transmitting permission signals ESA, ESB, and ESC.
2 is sent, this data D2 is sent to the terminal side circuit 6.
The demodulation circuit 62 converts the baseband signal BD2 into a baseband signal BD2, which is guided to the transmission control circuit 65 and stored.
As a result, the transmission control circuit 65 issues a command to the modulation circuit 61 to stop transmitting the transmission permission signal ESA, and causes the reception control circuit 63 to output the output strobe signal ST2 to the trunk line side circuit 2. On the other hand, when the trunk line side circuit 2 detects the strobe signal ST2 from the terminal side circuit 6 with the multiplex control circuit 24, this control circuit 24 returns a response signal AS2, and after that, the strobe signal ST2 sent from the terminal side circuit 6 is sent back. The baseband signal BD2 is output as the strobe signal ST.
Read at the falling edge of 2. Then, for this read baseband signal BD2, the transmission control circuit 23
After adding a flag and a frame check sequence (FCS) to form a frame, the signal is modulated by the modulation circuit 21 and sent to the trunk line 1. During this time, the terminal side circuit 6 confirms that the response signal AS2 from the trunk line side circuit 2 has been cut off, as shown in FIG. 7, and starts transmitting the transmission permission signal ESA to the terminal device A. The data (second frame) D2 sent from the terminal device A is read in the same way as the first frame data D2.

Now, while the data D2 from the terminal device A is being read and sent to the trunk line 1, data D4 arrives from the terminal device B, for example.
As a result, when the terminal side circuit 7 outputs the output strobe signal ST4 as shown in FIG. A.S.
After stopping the transmission of 2, send a response signal to the terminal side circuit 7.
Output AS4. Here, the output strobe signal
Needless to say, if the response signal AS2 is not output from the trunk line circuit 2 while ST2 is being output, the terminal side circuit 6 is not transmitting the transmission permission signal ESA to the terminal device A. In response to this, the terminal side circuit 7 sends the baseband signal BD4 to the trunk line side circuit 2, and turns off the output strobe signal ST4. As a result, the relay line side circuit 2 reads the baseband signal BD4 at the falling edge of the output strobe signal ST4, frames this baseband signal BD4 (FIG. 8B) in the transmission control circuit 23, and converts the baseband signal BD4 into a frame to the terminal side circuit. Following the baseband signal BD2 from 6 (FIG. 8A), it is sent to the trunk line 1 from the modulation circuit 21. During this time, the response signal AS2 is not output to the terminal side circuit 6 even if the output strobe signal ST2 is output, so naturally the transmission permission signal from the terminal side circuit 6 to the terminal device A is
No ESA transmissions are made. Therefore, no new data is transmitted from the terminal device A during this time. In addition, when the trunk line side circuit 2 finishes reading the baseband signal BD4, it outputs a response signal from the multiplex control circuit 24 to the terminal side circuit 7.
If AS4 is turned off and the output strobe signal ST2 is output from the terminal side circuit A as shown in Fig. 8, then
Instead, a response signal AS2 is output to the terminal side circuit 6. Therefore, the terminal side circuit 6 that receives this response signal AS2 naturally sends a transmission permission signal to the terminal circuit A.
Send ESA. As a result, the baseband signal BD2 (C in the figure) is sent out from the terminal side circuit 6.
This signal is framed by the transmission control circuit 23 and then sent to the trunk line 1 following the baseband signal (b). Thus, the transmission data D2 and D4 from the terminal devices A and B are alternately sent to the trunk line 1 for each frame. Here, terminal devices A and B
can send data at the same code transmission rate as when only one of A or B is communicating data. In other words, the modulation circuit of the terminal device can always keep its modulation speed constant. Note that the average code transmission rate from each terminal device to the branch control device at this time is naturally 1/2 of that when only one terminal is communicating data. FIG. 9a shows the above trunk line 1.
FIG. 4 is a timing diagram showing the state of sending data to the computer. Note that FIG. 9b shows a case where data D2, D4, and D6 are transmitted from terminal devices A, B, and C, respectively, and the multiplex control is such that data D2, D6 is transmitted only from terminal devices A and B, as described above. In the same way as when D4 is sent, the number of connected terminal devices is determined by the return and transmission timing of response signals AS2, AS4, AS6 and transmission permission signals ESA, ESB, ESC to each terminal side circuit 6, 7, 8. The transmission permission signals ESA, ESB, and ESC are varied according to the terminal equipment A, ESB, and ESC.
This can be done by transmitting to B and C alternately.
In addition, data D2 from each terminal device A, B, C,
When all transmissions of D4 and D6 are completed, transmission permission signals ESA and ESA are sent to each terminal device A, B, and C, respectively.
ESB and ESC are transmitted and the next data transmission becomes possible.

On the other hand, data MD2 arriving via trunk line 1
When distributing the data to each terminal device A, B, and C, it is done as follows.

When data MD2 multiplexed on a frame-by-frame basis is sent through the trunk line 1, for example as shown in FIG. After conversion, the transmission control circuit 26 converts the data into bit-parallel form.
to be memorized. Then, the separate reception control circuit 25 identifies the address information inserted in the data, and according to the identification result, outputs an output strobe signal ST1 to the corresponding terminal side circuit, for example 6, as shown in FIG. . On the other hand, the terminal side circuit 6
When detecting the output strobe signal ST1, it returns a response signal AS1. When this response signal AS1 is returned, the trunk line side circuit 2 receives the stored baseband signal BD1 from the separate reception control circuit 25.
When the signal level of this signal BD1 becomes stable, the output strobe signal ST1 is turned off.
As a result, the terminal side circuit 6 reads the baseband signal BD1 at the falling edge of the output strobe signal ST1, converts the read baseband signal BD1 into a frame in the transmission control circuit 64, and sends it to the terminal device A from the modulation circuit 61. do. Similarly, when the address information addressed to the terminal device B is identified in the trunk line side circuit 2, the separate reception control circuit 25 outputs a strobe signal to the terminal side circuit 7.
ST3 is sent out, and after the response signal AS3 is sent back, the baseband signal BD3 is sent out to the terminal side circuit 7. And this baseband signal BD3
is converted into a frame by the transmission control circuit 64 of the terminal side circuit 7 and then sent to the terminal device B from the modulation circuit 61. Thus, each data that has arrived via the trunk line 1 is distributed to each terminal side circuit 6, 7, 8 according to its address information, and is distributed to each terminal device A, B,
Sent to C. Furthermore, the transmission speed of each of the data to each terminal device A, B, and C can be made exactly the same as the transmission speed of the data MD2 on the trunk line 1 by the modulation circuit 61. Figure 11 shows each of the above data D.
FIG. 1 is a timing chart showing the transmission state of signals 1 and D3.

As described above, according to this embodiment, when data is transmitted from any terminal device, even if data has already been transmitted from another terminal device, the data can be transmitted at any time without waiting for the end of the data transmission. Transmission can begin. In addition, since only terminal devices that are in the data sending state are given a transmission permission signal to send data, the trunk line can be used efficiently and without waste, and as a result, data can be transmitted efficiently according to the number of terminal devices in the data sending state. In addition, transmission permission signals ESA, ESB, and ESC are sent to each terminal device to send data D.
Since the sending of data D2, D4, and D6 is controlled, there is no need to store a large amount of each data D2, D4, and D6 within the branch control device, which reduces the memory capacity of each part and makes the device less expensive. There are advantages that can be provided by

Note that the present invention is not limited to the above embodiments. For example, in the above embodiment, each terminal device transmits the same type of data, for example, a facsimile signal, but each terminal device transmits different data such as a facsimile signal, a telephone signal, or a teletype (TTY) signal. You can do it like this. Furthermore, for example, three terminal devices A, B, C
A, A, B, C,
Some terminals may be given priority over others, such as in the order of A, A, B, and C. It goes without saying that the number of terminal devices connected, the configuration of each circuit, etc. can be modified in various ways without departing from the gist of the present invention.

As detailed above, each data is multiplexed by varying the transmission timing of the transmission permission signal sent to each terminal device according to the number of terminal devices in the driving state, and the multiplexed data sent via the trunk line is multiplexed. According to the present invention, in which data is distributed to each terminal device according to its address information, even when data is being transmitted between a trunk line and any terminal device, this data transmission is Branching control in a data transmission system that can perform data transmission between other terminal devices and a trunk line at any time without waiting for the end of data transmission, and can perform efficient data transmission according to the number of terminals in the data transmission state. equipment can be provided. Further, according to the present invention, the terminal side circuit receives data frame by frame from the terminal device by supplying the transmission permission signal, temporarily stores the data of one frame in the storable first memory, and then At the same time, when the relay line side circuit completes reception of this one frame of data, a transmission permission signal is supplied to the terminal device, and the relay line side circuit transmits one frame of data to the plurality of terminal side circuits. The frame-by-frame data received from each terminal-side circuit is temporarily stored in a second memory capable of storing one frame of data, and then transmitted to the trunk line in a time-division manner in the order in which the terminal-side circuits have completed reception. Since branch control is performed by efficiently using one frame storage memory of each terminal side circuit and trunk line side circuit in the branch control device based on data transmission to the trunk line, each terminal in the branch control device A large-capacity memory for storing data from the device is not required, and an inexpensive device that can reduce the memory capacity can be provided.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention.
2 to 6 are block diagrams showing the configuration of the main parts of the control device. FIG. 2 is a block diagram of the terminal side circuit, and FIG. 3 is a block diagram of the terminal side circuit shown in FIG. 2. 4 is a block diagram of the reception and transmission control circuits, FIG. 4 is a block diagram of the relay line side circuit, FIG. 5 is a block diagram of the multiplex control circuit of the trunk line side circuit shown in FIG. 4, and FIG. is a block diagram of the transmission, separation/reception, and transmission control circuits of the trunk line side circuit shown in FIG. 4, and FIGS. FIG. 1... Relay line, 2... Relay line side circuit, 3, 4, 5...
Terminal line, 6, 7, 8...Terminal side circuit, D1, D2,
D3, D4, D5, D6, MD1, MD2...Data, BD1, BD2, BD3, BD4, BD5, BD
6...Baseband signal, ST1, ST2, ST3,
ST4, ST5, ST6...Output strobe signal, AS
1, AS2, AS3, AS4, AS5, AS6...response signal, ESA, ESB, ESC...transmission permission signal.

Claims (1)

[Claims] 1. In a data transmission system in which a trunk line and a plurality of terminal devices are branch-connected by a branch control device and data transmission is performed in frame units, the branch control device connects a plurality of terminal-side circuits and relays. The terminal side circuit is connected to each corresponding terminal device, receives data frame by frame from the terminal device by supplying a transmission permission signal to the terminal device, and receives data from the terminal device frame by frame. data is temporarily stored in a storable first memory and then sent to the trunk circuit, and when the trunk circuit completes receiving the one frame of data, the transmission permission signal is transmitted to the terminal device. The relay line side circuit is connected to each of the terminal side circuits and the relay line, and the terminal side circuits are connected to each of the terminal side circuits and the relay line, and the terminal side circuits are connected to each of the terminal side circuits in the order of the terminal side circuits that have completed receiving one frame of data in the plurality of terminal side circuits. Data transmission characterized by receiving one frame of data from a computer, temporarily storing the received frame-by-frame data in a second memory capable of storing one frame of data, and then transmitting it to a trunk line in a time-division manner. Branch control device in the system.