JPS61186047A - Data transmission system - Google Patents

Abstract

PURPOSE:To attain sure data transmission without confusing data by using a converting/decoding system different from the converting/decoding system for a signal in the 1st transmission mode so as to execute date transmission in the 2nd transmission mode. CONSTITUTION:A selection circuit 101 is provided to a data transmission control section at the sending side, one of data outputted from a scramble circuit 102 or a scramble circuit 103 is selected by the control of a control circuit 104 and sent to a line. The scramble circuits 102, 103 convert a signal depending on the different conversion system so as not to give an deviation in the code series of '1' and '0'. A data transmission control section at the reception side is provided with a selection circuit 201, which selects one of a data outputted from a descramble circuit 202 or a sending data SD sent from the data terminal equipment of the won station and sends it to the line based on a control signal outputted from a latch circuit 206.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to, for example, an improvement in a data transmission system in which two stations each having a modem with a time division multiplexing function transmit data via a line.

[Technical background of the invention]

A modem with time division multiplexing function is used in a data transmission system as shown in FIG. In the figure, l and 2 indicate modems with time division multiplexing function (hereinafter referred to as TS modems),
These TS modems 1 and 2 are connected via a line 3. TS modem 1.2 has data South America 41-44.
51 to 54 are connected. The TS modem 1.2 thus has four data channels and performs data transmission by time division multiplexing.

Such a TS modem 1.2 has a loopback function as one of the test functions to detect system abnormalities, and also has multiple data channels to improve data transmission efficiency. It has a similar CD transmission function.

First, the remote DC loop function, which is one of the return functions, will be explained. The remote DC loop function means that by operating a switch on the local modem, the signal is looped back at the terminal interface section of the other party's modem, and the signal emitted from the local modem is returned to the local modem via the other party's modem. It is a function that forms a loop to obtain. Conventionally, T.S.
In the modem, the above-mentioned remote DC loop function is activated when data transmission from the data terminal is not executed. ), data sent by the data terminal (SD
) from the TS modem to the remote DC/I/-
Data for forming a remote DC loop or data for canceling a remote DC loop is transmitted, and based on this data, the other party's TS modem controls the terminal interface so that a remote DC loop is formed or canceled.

Next, the pseudo CD transmission function will be explained. Pseudo-CD transmission function is an alternative to sending or cutting carriers because cutting off carriers for each data channel by time division multiplexing would require difficult control and reduce transmission efficiency. , a function to transmit predetermined data so that the other party's TS modem can send out the carrier detection signal CD to increase the data floor. Conventionally, in a TS modem, when the transmission request signal R8 from the local station 1 terminal turns off (on), data with a specific code indicating this is transmitted to the other party's TS modem, and the other party's TS modem receives the data 1. The carrier detection signal CD is turned off (on) and sent to the terminal.

[Problems with background technology]

However, when the TS modem configured as described above is actually used, the predetermined data and carrier detection signal C used for the above-mentioned remote
The same bood pattern as the code pattern of predetermined data used to turn on (off) D may appear as a code pattern of data other than the above. In such a case, the TS modem operates in the same way as the remote DC loop function or the pseudo CD transmission function, and there is a drawback that data that should have been sent to the end of the data is not sent. In particular, when the data code pattern is the same as the data code pattern for remote DC loop formation, a switch operation is performed on the sending side of the data to change the data code pattern for remote DC loop release. A problem has arisen in that the remote DC loop is not released unless data is transmitted, resulting in unnecessary data transmission.

[Purpose of the invention]

The present invention was made in view of the drawbacks of the conventional data transmission method, and its purpose is to prevent confusion between data transmitted in the first transmission mode and data transmitted in the second transmission mode. It is an object of the present invention to provide a data transmission method that allows data transmission to be performed without being compromised.

[Summary of the invention]

Therefore, in the present invention, data transmission in the second transmission mode is performed using a conversion/restoration method different from the signal conversion/restoration method in the first transmission mode.
The above objectives have been achieved.

[Example of the Invention] In this embodiment, the method of the present invention is used to realize a remote DC loop function in a TS modem.

FIG. 1 shows a data transmission control section provided for each data channel of a TS modem on the transmitting side. This data transmission control section is provided with a selection circuit 101, and the selection circuit 101 is a scramble circuit 102 or a scramble circuit 103.
One of the output data is selected under the control of the control circuit 104 and sent to the line. Scramble circuit 1
02 and the scrambling circuit 103 convert the signal using different conversion methods so that there is no bias in the code series of "1" and "0".

FIG. 2 shows an embodiment of the scrambling circuit.

This scramble circuit consists of a 12-stage shift register 15
and exclusive OR circuit (hereinafter referred to as EX-OR) 17.1
8 is the basic configuration. 23 is a protection circuit, and this protection circuit 23 consists of EX-ORs 19 to 21, an OR gate 22, and a counter 16. With only the basic configuration of the scramble circuit, "1" and "O" can be repeated without scrambling. There is a possibility that a return pattern will be output, so this is prevented. In the above, the basic configuration of the scrambling circuit is that the outputs of the 6th and 7th stages of the shift register 15 are led to the EX-OR18 via the EX-OR17, and the input signal SCRIN is connected to the EX-OR1g. A scrambled output signal 5CROUT is obtained by performing a logical operation. - In the protection circuit 23, the input signal 5CRIN, the output of the 8th stage of the shift register 15, and the output of the 12th stage of the shift register 15 are guided to the OR gate 22 via EX-ORs 19 and 20, respectively, and the output The counter 16 counts the number of consecutive "1"s, and when it reaches a predetermined number, the output of the counter 16 is set to H level for 1 bit, and this is the EX
- EX-ORI 7 of the basic component via OR21
It is configured to perform logical operations on the output of , forcing the repeating pattern to break.

If the scrambling circuit described above is the scrambling circuit 102 in FIG.
This can be achieved by obtaining the data from a stage other than the 7th and 7th stages. Furthermore, it is even better if EX-ORs 19 and 20 are obtained from sources other than the 8th and 12th stages of the shift register 15.

Therefore, when data of the same code pattern is input to the scramble circuits 102 and 103 configured as described above, the code patterns output are different from each other. A scramble circuit 102 scrambles transmission data SD transmitted from a data terminal of its own station. Further, the scramble circuit 103 includes an OR gate 10
Data for remote DC loop formation (specific code pattern) sent from the loop formation circuit 106 via 5, or data for remote DC loop cancellation sent from the loop cancellation circuit 107 (specific code pattern). Scrambling◎ When the signal generated by the operation of the switch 108 switches to a signal (H level) indicating remote DC loop formation, the control circuit 104 sends a control signal to the loop forming circuit 106 and the selection circuit 101 for a predetermined period of time, and scrambles the loop. The forming circuit 106 outputs data and controls the selection circuit 101 to select the output of the scramble circuit 103.The control circuit 104 also controls the signal generated by the operation of the switch 108 to be a signal (L) indicating remote DC loop cancellation. level], a control signal is sent to the loop release circuit 107 and the selection circuit 101 for a predetermined period of time, data is output from the loop release circuit 107, and the selection circuit 101 selects the output of the scramble circuit 103. control.

FIG. 3 shows a data transmission control section provided for each data channel of the TS modem on the receiving side. This data transmission control section is provided with a selection circuit 201, and this selection circuit 20
1 selects either the data output from the descrambling circuit 202 or the transmission data SD transmitted from its own data terminal based on the control signal output from the latch circuit 206, and sends it to the line. The descrambling circuits 202 and 203 descramble (restore) the signals sent via the line, and the descrambling circuit 202 can restore the signal scrambled by the scrambling circuit 102 to the original signal. The descrambling circuit 203 can restore the signal scrambled by the scrambling circuit 103 to the original signal. These descrambling circuits 202 and 203 are designed corresponding to the scrambling circuit shown in FIG.

The output of the descrambling circuit 203 is given to a loop formation detection circuit 204 and a loop release detection circuit 205. The loop formation detection circuit 204 is a descrambling circuit 2
When the data output from 03 is a code pattern indicating remote DC loop formation, a control signal is output, and the loop release detection circuit 205 detects that the data output from the declarator/pull circuit 203 indicates remote DC loop release. When it is a code pattern, a control signal is output.

The control signals output from the loop formation detection circuit 204 and the loop release detection circuit 205 are latched to the latch circuit 206 and applied to the selection circuit 201.

As described above, the operation when two TS modems having the data transmission control units shown in FIGS. 1 and 3 transmit data via a line will be described.

By initial setting, the selection circuit 101 is selected from the control circuit 104.
A control signal is output to select the output of the scramble circuit 102, and a control signal output from the loop release detection circuit 205 is latched to the latch circuit 206. The transmission data SD to be sent is selected. Therefore, each TS modem modulates, demodulates, and scrambles and descrambles signals for data transmission by data terminals. Although not shown, the output of the descrambling circuit 202 is transmitted to the own data terminal as received data RD.

In addition, for remote DC loop formation, switch 10
8 is operated, under the control of the control circuit 104, data indicating remote DC loop formation outputted from the loop forming circuit 106 reaches the scramble circuit 103 via the OR gate 105, is scrambled, and is sent to the selection circuit 101.
be sent to the other party's TS modem via In the destination TS modem, the descrambling circuit 203 restores the data to the data before being scrambled. Upon receiving this, the loop formation detection circuit 204 detects data indicating the formation of a remote DC loop and outputs a control signal.

As a result, this control signal is latched in the latch circuit 206, and the selection circuit 201 selects the output of the descrambling circuit 202 based on the output of the latch circuit 206. On the other hand, in the TS modem that has transmitted the data indicating remote DC loop formation, the control circuit 104 controls the selection circuit 101 after a predetermined period of time so that the output of the scrambling circuit 102 is sent to the line. As a result, the transmitted data SD (from the own data terminal of this TS modem) is folded by the descrambling circuit 202 and selection circuit 201 of the other TS modem, and then returned (
That will happen. Further, when the switch 108 is operated to release the remote DC loop, the remote DC output from the loop release circuit 107 is controlled by the control circuit 104.
Data indicating C-loop cancellation reaches the scramble circuit 103 via the OR gate 105, is scrambled, and is transmitted to the partner TS modem.

In the destination TS modem, the descrambling circuit 203 restores the data to the data before being scrambled. The loop cancellation detection circuit 205 receives this,
Detects data indicating remote DC loop release and outputs a control signal. As a result, this control signal is latched in the latch circuit 206, and the selection circuit 201 selects the transmission data SD transmitted from the data terminal of its own station based on the output of the latch circuit 206. In this embodiment, the code pattern scrambled by the scrambling circuit 103 used for the remote DC loop function is the same as the code pattern of the original data by the descrambling circuit 203 used for the remote DC loop function. However, the code pattern of the original data is not restored by the descrambling circuit 202; on the contrary, the code pattern scrambled by the scrambling circuit 102, which is used for normal transmission, is not returned to the original code pattern for normal transmission. The descrambling circuit 202 used returns the code pattern of the original data, and the descrambling circuit 2
03 does not return to the original data code pattern.

Therefore, even if the data code patterns in each transmission mode are the same, accurate data transmission can be performed without data confusion.

It should be noted that the present invention can be applied not only to the pseudo CD transmission function but also to data transmission having two transmission modes.

〔Effect of the invention〕

As explained above, according to the present invention, data used in each of the two transmission modes is not mixed up (and accurate data transmission is possible).

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a data transmission control section provided in a modem on the transmitting side of data transmission according to the present invention, and FIG.
FIG. 3 is a block diagram of a data transmission control unit provided in a modem on the receiving side of data transmission according to the present invention, and FIG. 4 is a block diagram of a data transmission system using a TS modem.

Claims (2)

[Claims] (1) In a data transmission system in which two stations transmit data via a line, the control data that controls the line connection is processed using a conversion/restoration method that is different from the signal conversion/restoration method used during normal data transmission. A data transmission method characterized by converting and restoring signals before transmission. (2) The data transmission method according to claim (1), wherein the control data is data instructing formation of a remote DC loop or release of the remote DC loop.