JPH02248129A - Timing correcting system - Google Patents

Abstract

PURPOSE:To extend a MODEM cable between a MODEM and a branching filter by allowing the branching filter to retard a transmission signal element timing signal from the MODEM for the prescribed time and sampling a transmission data synchronously with a signal from a data terminal equipment and sending the resulting signal to the MODEM synchronously with the signal from the MODEM. CONSTITUTION:The delay time tab of a MODEM cable 5 and the delay time tac of a receiver 15 of an MSD 30 are given to a signal ST2c as a timing at the point (c) of a branching filter MSD 30 based on a signal ST2a being an ST signal outputted from the point (a) of a synchronous MODEM 2a of a timing correction system. Then the delay time tcd of a driver 17 of the MSD 30 and the delay time tde of a DTE cable 6 are given to an ST2e at the point (e) of a data terminal equipment DTE 4a as the timing. Moreover, a transmission data SDe from the DTE 4a is retarded by the delay time tf of a receiver 22, a noise suppression circuit 24 and a driver 23 and a timing retarded by the delay time tde of the cable 6 and the delay time tdc of a receiver 18 of the MSD 30 is given to a signal SDc1.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a timing correction method, and particularly to a modem device (hereinafter referred to as "modem j") in a data communication system.
The timing between the transmission signal element timing signal (hereinafter referred to as "rST2 signal"), which is a modem interface signal installed between the branching device (hereinafter referred to as rMsDJ) and the data terminal equipment (hereinafter also referred to as rDTEl), and the transmitted data. The present invention relates to a timing correction method suitable for performing correction.

[Conventional technology]

In conventional general data communication systems, for example, as disclosed in Japanese Patent Application Laid-Open No. 62-90059,
According to the ISC-6361 standard, the data transmitted from the data terminal device was sampled by the ST2 signal in the modem in accordance with the interface between the modem and the communication control device and the data terminal device, so it was not connected to the modem mentioned above. cables, MSD and D
It was necessary to limit the length of the cable so that the timing between the ST2 signal and the transmitted data would not be disrupted due to the TE delay time. This was especially important as transmission speeds increased.

This will be explained in detail below using the drawings.

FIG. 5 shows host 1 to synchronous modem 2 and dedicated line 7.
from MSD3 to CHI and C
This shows a data communication system in which a DTE4 is connected to an H2.

In the connection of the synchronous modem 2, MSD 3, and DTE 4 as described above, the ST2 signal at point a of the synchronous modem 2 is connected to 5T2a,
If the ST2 signal at the 0 point of DTE4 is 5T2e, D
TE4 transmits transmission data SDe in synchronization with 5T2e, and the transmission data from DTE4 is received as reception data RD by synchronous modem 2 via MSD3, and O of 5T2a is sent.
The data is determined by sampling the received data at the timing from N to OFF.

In this case, as can be understood from FIG. 6, the sum of modem cable delay time td□, MSD delay time td2゜DTE cable delay time td3, and DTE delay time td is T2=2(td1+td2+td3)+td4, which is T1/
If it is larger than 2, the received data will be judged incorrectly, so EIA
(Electronic Industries Association of America) standard R8334 stipulates that the timing from ON to OFF of the ST2 signal at point a of the synchronous modem 2 and the conditions for determining the received data are to be maintained at 25% or more of T1.

[Problem to be solved by the invention]

In the above conventional technology, the timing shift between the ST2 signal and the transmitted data was prevented by limiting the cable length, so no consideration was given to extending the cable length, and the modem cable and DTE cable could not be extended. There was a serious problem.

The present invention has been made in view of the above circumstances, and its purpose is to solve the above-mentioned problems in the conventional technology, correct the timing of the ST2 signal and the transmitted data, and correct the timing between the modem cable and the DTE cable. The object of the present invention is to provide a timing correction method that enables extension of the timing.

[Means to solve the problem]

The above-mentioned object of the present invention is to provide a data terminal including a modem and a data terminal device, and an MSD installed between the modem and the data terminal device, which branches a modem interface signal into DC and connects the data terminal device to the branch side. In the communication system, a delay means is provided in the MSD to transmit the ST2 signal from the modem to the data terminal device as it is, and transmit data transmitted from the data terminal device in synchronization with the ST2 signal. A timing correction method or modem characterized in that the ST2 signal is sampled by a signal delayed for a certain period of time by a delay means in the MSD, and then synchronized with the ST2 signal and transmitted as transmission data to the modem. and a data terminal device, and an MSD that is installed between the modem and the data terminal device, branches the modem interface signal into a DC branch, and connects the data terminal device to the branch side. A delay means is provided to transmit the ST2 signal from the modem to the data terminal device as is, while transmitting data transmitted from the data terminal device in synchronization with the ST2 signal to the ST2 signal from the modem.
This is achieved by a patented correction method characterized in that the T2 signal is sampled using a signal delayed for a certain period of time by a delay means within the modem.

[Effect]

In the first timing correction method according to the present invention,
The MSD delays the ST2 signal from the modem for a certain period of time, samples the transmission data synchronized with the ST2 signal from the DTE, and transmits it to the modem in synchronization with the ST2 signal from the modem. It becomes possible to correct the delay time caused by the MSD cable, and it becomes possible to make the DTE cable between the MSD and the DTE and the modem cable between the modem and the MSD sufficiently long.

Also, in the second timing correction method according to the present invention, the ST2 signal is delayed for a certain period of time in the modem, and the
Since the transmitted data is sampled in synchronization with the ST2 signal from the TE, MSD and DTE, modem and M
It is now possible to correct the delay time caused by the SD cable, and the DTE cable between the MSD and DTE, the modem and the MSD
This allows the modem cable between the two to be sufficiently long.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows one embodiment of the present invention, and is a block configuration diagram when timing is determined in the MSD.
The figure is a time chart showing the operation. In FIG. 1, 2a and 4a indicate the main parts of the synchronous modem 2 and DTE 4, respectively, from which only the parts necessary for explaining the operation of this embodiment are extracted, and 30 is a characteristic part of this embodiment. This shows the main parts of the MSD.

The main part of the synchronous modem 2a (hereinafter simply referred to as "synchronous modem 2")
clock source 11.aJ). Driver 12.
Sampling circuit 13. A receiver 14 is provided within the DTE main section 4a (hereinafter simply referred to as rDTE4aJ). Driver 23° noise suppressor circuit 24. The synchronization circuit 25 also connects the MSD main section 30
Inside are receivers 15 and 18. Drivers 16 and 17. Delay circuit 19. Synchronous circuit 20. A sampling circuit 21 is provided.

An outline of the operation of this embodiment is as follows.

First, the synchronous modem 2a outputs the ST2 signal as 5T2a from the clock source 11 via the driver 12, receives the received data RD by the receiver 14, and when the clock source 11 turns from ON to OFF, the received data is sent to the sampling circuit 13. Make a determination.

The MSD 30 receives the ST2 signal (ST2a) output from the synchronous modem 2a as 5T2c by the receiver 15, outputs it from the driver 17, and also outputs it from the DTE 4a.
5, the receiver 18 receives the transmission data SD from
The signal 5Dc2, which is sampled by the sampling circuit 21 at the timing from ON to OFF of S Tut, which is obtained by delaying Dcl by a certain period of time from the aforementioned 5T2a by the delay circuit 19, is synchronized by the synchronization circuit 20 at the timing from OFF to ON of 5T2c. The resulting signal 5Dc3 is transmitted from the driver 16 to the synchronous modem 2a.

In addition, in DTE4a, ST2 from MSD30
The signal (ST2c) is received by the receiver 22, synchronized by the synchronization circuit 25 at the timing of the synchronization signal passing through the noise suppressor circuit 24 from OFF to ON, and then sent to the driver 2.
3 to the MSD 30 as SD.

Hereinafter, a detailed explanation will be given using the operation timing chart of the above embodiment shown in FIG.

ST signal 5T2a output from point a of synchronous modem 2a
is the delay time tab of the modem cable 5 and the delay time tb of the receiver 15 of the MSD30 at the 0 point of the MSD30.
c becomes the timing of 5T2c, and e of D T E4a
At this point, the delay time tcd of the driver 17 of the MSD 30 and the delay time tde of the DTE cable 6 are at a timing of 5The.

Further, the transmission data SDe from the DTE 4a is transmitted to the receiver 22. Noise suppression circuit 24. The timing at which the output is delayed by the delay time tf of the driver 23 and further delayed by the delay time tde of the DTE cable 6 and the delay time tdc of the receiver 18 of the MSD 30 is 5Dc1.

On the other hand, STl delayed by the delay time td by the delay circuit 19
5Dc2 is obtained by sampling from ON to OFF and correcting the timing. Since this 5Dc2 can be absorbed by the delay time td due to the length of the DTE cable 6, the delay time tde due to the length of the DTE cable 6 is ( t cd+2 t de+ t f+ t dc
-t d)<0.25T From 1, the DTE cable 6 can be stretched within the range that satisfies the above formula.

Next, the 5Dc2 is synchronized by the timing signal 5T2c of the synchronization circuit 20, outputs the timing of the 5Dc3, and transmits it as the reception data RD of the synchronous modem 2a. In this case, the allowable delay time ta due to the modem cable 5
From (tbc+2tab+tab)<0.25T 1, b is (0,25T 1-(t bc+ t cb)) t a
b<, and the modem cable 5 can be extended within the range that satisfies the above equation.

According to the above embodiment, in M S l), the signal obtained by delaying the ST2 signal from the synchronous modem and the delay time due to the DTE cable can be offset, so there is an effect that the length of the DTE cable can be extended. . Also, -dan,
Since the MSD uses ST2 from the synchronous modem to perform synchronization using the synchronous circuit, there is an advantage that the length of the modem cable can be extended.

FIG. 3 shows another embodiment of the present invention, and is a block diagram in which timing is determined in a synchronous modem, and FIG. 4 shows time charts 1 to 1 showing its operation.
It is. In FIG. 3, 3a and 4a respectively indicate the main parts of the above-mentioned MSD 3 and DTE 4, from which only the parts necessary for explaining the operation of this embodiment are extracted.
Reference numeral 60 indicates the main part of the synchronous modem, which is a characteristic part of this embodiment.

In the above-mentioned synchronous modem 60, the above-mentioned clock source 11,
Driver 12. Sampling circuit 13. In addition to the receiver 14, a delay circuit 65 is provided. Note that the MSD main section 3a (hereinafter simply referred to as rMSD 3aJ) includes receivers 15, 18. The drivers 16 and 17 are D
In the TE 4a, there is a receiver 22. Driver 23, noise suppressor circuit 24. A synchronization circuit 25 is provided respectively.

In this embodiment, the modem cable 5 and the DTE cable 6 are extended by sampling the received data in the sampling circuit 13 of the synchronous modem 60 using a timing signal obtained by delaying the clock source 11 by a fixed period of time by the delay circuit 65. This is an example.

As shown in the timing chart of FIG. 4, the allowable delay time of the delay time tab due to the modem cable 5 and the delay time tde due to the DTE cable in this case is (tha+2tab+tbc+tcd+2tde+
tf t dc+t cb+ t ah -t d)<
From 0.25T 1, tab + tde is obtained, and the modem cable 5 and DTE cable 6 can be extended within the range that satisfies the above formula.

That is, the modem cable 5 or DTE cable 6 can be extended by the delay time td caused by the delay circuit 65 of the synchronous modem 60.

According to the above embodiment, in a synchronous modem, the signal obtained by delaying the ST2 signal and the delay time caused by the modem cable and the DTE cable can be offset, so there is an effect that the length of the modem cable or the DTE cable can be extended. .

It should be noted that the above-mentioned embodiment is shown as an example, and it goes without saying that the present invention should not be limited thereto.

〔Effect of the invention〕

As described above in detail, according to the present invention, in the MSD, the signal obtained by delaying the ST2 signal from the synchronous modem and the delay time due to the DTE cable are canceled out, or the ST2 signal is delayed in the synchronous modem. This is a significant improvement in that it is possible to realize a timing correction method that allows the timing of the ST2 signal and the transmitted data to be corrected by canceling out the delay time caused by the modem cable and the DTE cable, thereby making it possible to extend the modem cable or DTE cable. This has the following effects.

[Brief explanation of drawings]

Fig. 1 is a block configuration diagram when timing is determined in an MSD which is an embodiment of the present invention, Fig. 2 is a time chart showing its operation, and Fig. 3 is another embodiment of the present invention. A block configuration diagram when timing is determined in a synchronous modem, FIG. 4 is a time chart showing its operation, FIG. 5 is a configuration diagram showing a conventional data communication system, and FIG. 6 is a time chart showing its operation. It is. 1: host, 2.2a: synchronous modem, 3.3a: MSD
, 4.4a: DTE, 5: Modem cable, 6: D
TE cable, 7: Dedicated line, 8: Host cable, 1
1: Clock source, 12, 16. 17 and 23: Driver, 13 and 21 = sampling circuit, 14, 15. 18
and 22: receiver, 19 and 65: delay circuit, 20 and 25 = synchronization circuit, 24: noise suppressor circuit.

Claims (1)

[Claims] 1. A modem device (modem) and a data terminal device, and a modem interface signal installed between the modem and the data terminal device, capable of branching the modem interface signal to direct current and connecting the data terminal device to the branch side. In a data communication system having a branching device (MSD), a delay means is provided in the MSD, and a transmission signal element timing signal (ST2 signal) from the modem is directly transmitted to the data terminal device. The transmission data transmitted from the device in synchronization with the ST2 signal is transmitted from the ST2 signal to the M
A timing correction method characterized in that after sampling is performed using a signal delayed for a certain period of time by a delay means in the SD, the signal is synchronized with the ST2 signal and transmitted as transmission data to the modem. 2. A modem and a data terminal device, and a branching device (MSD) installed between the modem and the data terminal device, which branches the modem interface signal into DC and connects the data terminal device to the branch side. In the data communication system, a delay means is provided in the modem to transmit a transmission signal element timing signal (ST2 signal) from the modem to the data terminal device as it is, while A timing correction method characterized in that synchronously transmitted transmission data is sampled using a signal obtained by delaying the ST2 signal by a certain period of time by a delay means in the modem.