JPS59228445A - Data transmission system - Google Patents

Abstract

PURPOSE:To reduce the number of signal lines between the network side and the terminal side by providing separately an interface converting device to the network side and the terminal side in connecting a data exchange network to data terminal devices in accordance with the protocol of the CCITT recommendations 21. CONSTITUTION:In connecting a data terminal device DTE having an X21 interface and a line terminator DCE of the data exchange network, interface converting devices CONV1, 2 are provided between both devices. The converting device CONV1 multiplexes the information on lines T and C from the terminal device DTE of the X21 interface, converts the result to manchester codes and the result is transmitted further to a line L while its transmitting speed is increased. On the other hand, the information from the device DCE is converted to Manchester decoding and demultiplexed into the information of the lines R and I and the result is transmitted to the terminal device DTE. The CONV2 of the device DCE conducts the similar operation. Thus, the number of signal lines between the terminal device DTE and the device DCE is decreased from 5 lines (used in a conventional system) into 1 line.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a data transmission system between a data exchange network and a data terminal, and particularly relates to a CCITT recommendation X21 interface.
The present invention relates to a transmission method suitable for connection according to a protocol.

[Background of the invention]

The CCITT recommends an interface defined by X21 as an interface between a public data switching network and a synchronous data terminal. This interface is a five-way interface between data terminals (DTE) and line termination equipment (DCE) of a data exchange network (hereinafter referred to as the network) as shown in Figure 1.
Requires a pair of signal lines. That is, transmission data line T from DTE to DCB, control line C from DTP to DCE, reception data line R from DCE to DTE, indication line I from DCE to DTE, and signals from DCE to DTE. This is an element timing line S.

As described above, when constructing a data communication system that connects terminals having this interface, there is a drawback that the number of construction cables increases because the number of lines between the terminals is large.

[Purpose of the invention]

An object of the present invention is to provide a system that eliminates the above-mentioned drawbacks and reduces the number of signal lines.

[Summary of the invention]

In other words, a multiplex circuit, a demultiplex circuit, a Manchester encoding circuit, and a Manchester decoding circuit are installed on the data terminal (DTE) having the X21 interface protocol and the circuit terminating equipment (DCE) side, which is an interface on the network side. , and a transmission direction control circuit, are provided on the network side and the terminal side, respectively, and multiplexes the data signal and the control signal, further performs Manchester encoding, and compresses it on the time axis. two pairs of wires from DCE to D
By making data to the TE and data from the DTE to the DCE alternately usable, the number of signal lines between the DTE and DCE is reduced.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is an example of a connection between a terminal (DTE) having an X21 interface and a network line termination equipment (DCE) according to the present invention. The interface conversion device IC0NVI is
After multiplexing the T line and C line information from the DTE at the 21 interface, it is Manchester encoded, the transmission speed is further increased, and it is sent to the L line, while the DCE
The information is Manchester-decoded, demultiplexed into R-line and T-line information, and sent to the DTE.

On the other hand, interface conversion circuit 2 on the DCE side C0NV2
After multiplexing the information on the R and T lines from the DCE, the information is Manchester-encoded, the transmission speed is further increased, and the information is sent to the L line, while the information from the DTE is Manchester-decoded and transmitted to the T and C lines. The information on the line is demultiplexed and sent to the DCE. In the present invention, D
Information from TE to DCE and information from DCE to DTE alternately use one L line.

Next, the operation of one embodiment of the present invention will be explained using FIGS. 3 and 4. FIG. 3 shows an example of the circuit configuration of C0NVI and C0NV2. Further, FIG. 4 shows an example of a time chart of transmission and reception between C0NVI and C0NV2. Information on the R line transmitted from the network side according to the timing of the signal element clock line S is
It is first received by the receiving system register R8RN. When the counter CNTN counts the number of capacity bits of R8RN with the clock S signal, it outputs a signal 1, transfers the data on the R line from R8RN to the transmission shift register 5SRN, issues a transmission request to the Manchester encoding circuit ENCN, and , the transmission direction control circuit 2 is set to enable transmission from C0NV2 to C0NVI. When the Manchester encoding circuit ENCN receives signal 1, it Manchester encodes the information on the R line and the T line and transmits it to C0NVI via the multiplex circuit MPXN. At this time, C0
The transmission from NV2 to C0NVI is sent in frames, and the transmission rate is higher than the actual data transmission rate. The time relationship of data transmission will be explained using FIG. From state 1, the information on the R line is transferred to the receive shift register R.
8RH and in state 2, CNTN generates signal 1. ENCN now starts transmitting and ends in state 3. When the Manchester encoding circuit ENCw finishes transmission, it sends a transmission completion signal 3 to the transmission direction control circuit 2, and
Set 0NV2 to receive state from the L line.

When C0NV2 receives data from the L line, it inputs it to the data input DIT of the Manchester decoding circuit DECT, decodes the Manchester code, and outputs it to the deniter output I)QT. Also at this time, the decode shift clock D8C
Output T. The output from DOT is multiplexed with R-ray information and X-ray information, so this is sent to a demultiplexer circuit.

DMPXT separates the information into R line and T line information. Also,
DMPXT creates a signal element clock line S from the decode shift clock. When the Manchester decoding circuit completes reception of one frame, it sends a reception completion signal 6 to the transmission direction control circuit 5. When the transmission direction control circuit 5 receives the signal 6, it sends out the signal 4 and C0
Nv1 is made ready for transmission, and a transmission request is issued to the transmission request manual 5RIT of the Manchester encoding circuit ENCT. The Manchester encoding circuit ENCT is
When a transmission request is received, the information on the T line and the C line is multiplexed, then Manchester encoded and sent to the L line. This process is exactly the same as in the case of the R line and T line of C0NV2. When the Manchester encoding circuit ENCT completes transmission, it sends a transmission completion signal 7 to the transmission direction control circuit 5, and the transmission direction control circuit 5 sets C0NV2 to the receiving state from the L line and receives reception from C0NV2. . The transmission of C0Nv1 described above corresponds to states 6 to 8 in FIG. 4.

When C0NV2 receives the data of C0Nv1 from Jl, it decodes the Manchester code and outputs the data DON.
It also outputs a decode shift clock DSCN and sends it to the demultiplexer circuit DMPXN. The demultiplex circuit DMPXN separates the T line and C line information from the data from the DON and transmits it to the network. At this time, the output of the T line is the signal element clock line S
Synchronize with.

In this embodiment, the transmission speed on the L line is determined by the clock CLKN for transmission from C0NV2 to C0NVI, and determined by the clock CLKT for transmission from C0NVI to C0NV2. In the present invention, transmission in both directions must be completed from state 1 to state 2, and therefore clocks CLKN, C
The LKTo speed needs to satisfy this condition.

In this example, C0NVI and C0NV2 are
Although shown as an external device for DTE and DCE, C0
Nv1 or C0Nv2 respectively DTE and DC
It is also possible to provide it within E. At this time, clock C
It is also possible to omit LKN by receiving it from the DCE as a clock that is an integer multiple of the signal element clock line.

〔Effect of the invention〕

According to the present invention, when connecting a data exchange network and a data terminal using the CC Engineering TT Recommendation This has the effect of reducing the number of signal lines between networks.

[Brief explanation of the drawing]

Figure 1 is a conventional connection diagram in the CCITT recommendation X21 interface protocol, Figure 2 is a diagram to which the present invention is applied, and Figure 3 is a diagram of interface converters C0NVI, C
FIG. 4, which is a diagram showing the configuration of 0NV2 and its connections, is a diagram showing the time sequence of data transmission and reception in the present invention. DTE...Data terminal equipment, DCE...Network side line termination equipment, C0NVI, C0NV2...Interface converter, ENCN, ENCT...Manchester encoding circuit, DECN, DECT...Manchester decoding circuit, MPXN, MPXT...Multiplex circuit, D
MPXN. DMPXT... Demultiplex circuit, 2, 5...
Transmission kudzu 1 diagram

Claims (1)

[Claims] In a data exchange system that connects a data exchange network and data terminals according to a predetermined procedure, an interface device consisting of a Manchester encoding circuit, a Manchester decoding circuit, a multiplexing circuit, a demultiplexing circuit, and a transmission direction control circuit is used. , provided on the data exchange network side and the data terminal side, respectively, and realized by one pair of wires by connecting via the above device.