JPH02305044A - Data transmission system - Google Patents

Abstract

PURPOSE:To constitute this system so that the transmission side can always understand the latest state of the reception side, and the transmission/reception procedure can be advanced without a delay by transmitting the state of the reception side again at a stage that the transmission of data of one group is ended. CONSTITUTION:In a phase D, a transmission station transmits an MPS(Multi-page signal) frame to a reception station with the intention of executing the continuous transmission, and when the MPS frame is received, the reception station transmits an MCF(Message Confirmation), RTP(Retrain Positive) or RTN(Retrain negative) frame, and a DIS(Digital Identification Signal) frame at that time point to the transmission station in accordance with a result of reception of an image in the previous time. By this DIS frame, it is shown that there is no receiving capacity. Accordingly, the transmission station does not transmit continuously an image but enters immediately into a phase E, transmits a DCN(Disconnect) frame and cuts off the circuit. In such a way, whenever the data transmission of one unit is ended, a master station can know only a reception state of a slave station but also the latest state of the slave station, and the transmission procedure can be advanced without a delay without necessitating a special time.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a data transmission system.

[Prior Art] Conventionally, as a protocol for transmitting images via a telephone line, for example, the GIII standard uses the T0n protocol recommended by CCITT. In T0n,
The facsimile transmission procedure is divided into five phases as shown in FIG.

Phase A involves connecting the facsimile machine to a telephone line in order to place or respond to a telephone call. Phase B
In this step, the functions of the receiving station are identified, the transmitting station issues a receive command to the receiving station, and the receiving station responds to the receive command to the transmitting station. In phase C, image data is transmitted and received.

In phase D, the images transmitted in phase C are verified. After phase D, the process returns to phase B or C to continue transmitting the next image, or proceeds to phase E, where the line is disconnected.

The control signals used in each phase will be explained in detail. G
In the 11l facsimile, control signals for controlling transmission procedures are expressed in a format similar to an HDLC frame, as shown in FIG. i.e. one or more bytes of start flag, address field, control field, facsimile control field (FCF)
, facsimile information field (F
rF), a frame check sequence, and one or more bytes of termination flag. The address field data is FFH and the control field data is COF+ or C8H. The frame check sequence is an error detection code for data from the data immediately after the start flag to immediately before the frame check sequence. In GnI facsimile, FC
Phase B using F and PIF information.

The FCF indicates the type of frame, and the PIF contains individual information regarding the FCF. In the following explanation, control frames will be called by FCF names.

The general signal flow in phases B, D, and E is shown in FIG. In Phase B, the receiving station evaluates its own transmission and reception capabilities using DIS (Digital + Dentific
ation Signal) frame to the transmitting station (Fig. 4 (1)). The transmitting station determines the transmission mode from the information in the DIS frame of the receiving station, and uses DCS (Digital
Specify the reception mode in the CommandSignal) frame and request reception from the receiving station (Figure 4 (2))
. After the DCS frame, the modem training signal T
Send a CP and wait for a response from the receiving station. The receiving station is T
Declares to the transmitting station whether the CP reception status is good or bad. In other words, the receiving station uses CFR (Conf ir) when the reception condition is good.
mation To Receive) frame,
Failure To Tra
in) Transmit the frame to the transmitting station ((3) in FIG. 4).

When the transmitting station receives a CFR frame, it starts image transmission in phase C, and when it receives an FTT frame, it starts over from the first DCS frame in phase B. However, the FrF of this DCS frame usually specifies a speed slower than the previous modulation/demodulation speed. Furthermore, the transmitting station may receive the DIS frame again from the receiving station after the DCS frame and the TCF frame.

This occurs when the receiving station fails to receive a DCS frame or a TCF frame from the transmitting station. in this case,
The transmitting station starts transmitting the DCS frame again.

When the image transmission is finished, the transmitting station enters Phase D. To continue image transmission, use MPS (Multi-page
Signal) frame, EOP (En
d of Procedure), when changing the transmission mode or changing the function of the transmitting station or receiving station,
The OM (End of Message) is transmitted to the receiving station ((4) in FIG. 4).

When the receiving station finishes image transmission and receives these frames, it sends the reception status of the image data received in phase C to MCF (Message Confirmation).
frame, RTP (Retrain Po5it, IV
e) Frame or RTN (Retrain Negat)
ive) frame to notify the transmitting station (Fig. 4 (
5)). Here, the MCF frame indicates that the image data was received normally, the RTP frame indicates that an error occurred but the image quality was at least acceptable, and the RTN
The frame indicates that many errors occurred and the image could not be received.

When the transmitting station transmits an MPS frame to the receiving station with the intention of continuing image transmission in phase D, and the receiving station responds with an MCF frame, it usually starts the next image transmission from the beginning of phase C. . Receiving station is R
When responding with a TP or RTN frame, the next image transmission starts from phase B DCS frame transmission (FIG. 4 (2)).

EO with the intention of the transmitting station finishing image transmission in phase D
When a P frame is transmitted to a receiving station, a DCN (Disconnect) frame is transmitted to the receiving station after waiting for a response from the receiving station, and the line is disconnected. However, if the response from the receiving station is an RTN or RTP frame,
If there is a capability to retransmit the previously transmitted image data, it is possible to retry the transmission of the DCS frame in phase B. This is the same even when an MPS frame is received or a 20M frame is received.

When the transmitting station intends to exchange the transmitting and receiving functions with the receiving station in phase D, it transmits a 20M frame to the receiving station. When the receiving station receives the 20M frame, the MCF, RT
After transmitting either N or RTP frame to the transmitting station,
After 6 seconds have elapsed, the station returns to the beginning of phase B and transmits its own DIS frame. After receiving the response to the 20M frame, the transmitting station returns to the beginning of Phase B, waits for the other station's DIS frame, and upon receiving it, if it learns from the content that the other station has transmission capability, it sends a DTC ( Digital Transmit Com
mand) frame can be used to inform the partner station of the capabilities of the eye station and to request image transmission.

The DTC frame differs from the DISIS frame only in FCF. A station that receives a DTC frame becomes a transmitting station and can issue a request to receive a DCS frame to the other station. The above transmission procedure is illustrated in FIG.

[Problems to be Solved by the Invention] In the GIII facsimile protocol described above, the state of the other party (receiving) station can only be known from the DISIS frame sent from the other party in phase B. In Phase D, the information from the receiving station only includes information about the previous image transmission in Phase C.

Therefore, even if the receiving station runs out of recording paper after phase C or overflows the capacity of the buffer memory for temporarily storing data, the transmitting station cannot know the status. Therefore, when the transmitting station continuously transmits, it enters phase C immediately after phase D, so even though the receiving station cannot receive image data, it may continue transmitting images until the continuous transmission ends. There is sex. In order to avoid this, it is conceivable that the receiving station transmits an RTP frame to the transmitting station in Phase D instead of the MCF frame. The transmitting station RTs in phase D.
When a P frame is received, normally the next image transmission is started from phase B DCS frame transmission without suddenly entering phase C. If the partner station transmits its own DIS frame at this time, the transmitting station can know the status of the partner station and can initiate appropriate abnormality processing.

However, in this case, there is a drawback that extra time is required for the transmitting station to transmit the DCS frame and TCF frame. Also, even though the receiving station received normally, the MC
Declaring RTP frames instead of F frames to the transmitting station is a method that deviates from the original functionality.

Another extreme example of a workaround is that the receiving station may transmit a DCN frame in Phase D and cut off the line, but the result of image transmission in Phase C may be communicated to the transmitting station. I can't. Furthermore, if the receiver does not have the receiving capability but has the transmitting capability, further transmission will not be possible using this method.

In addition to a situational change in which the receiving station loses its receiving capability, the transmitting capability may also change. For example, in the first phase B,
The receiving station does not have image transmission capability, and the DISlS frame r
Suppose that F expresses that it has no transmission capability and informs the transmitting station. After Phase C, if the user at the receiving station becomes capable of transmitting images by setting a document, etc., the transmitting station determines the transmission procedure based on the information from the previous Phase B, so the other station cannot There is a risk that it will determine that there is no transmission capability and will transmit a 20M frame, proceeding to phase E without attempting to transmit or receive, and cutting off the line.

As a way to avoid the above two types of problems on the sending side,
A possible method is to always transmit a 20M frame to the receiving station in phase D and wait for the other station to send a DISIS frame. In this way, the latest DKS at that time can be known, and after receiving the other party's DIS, it is sufficient to request reception (transmission) using a DCS (or DTC) frame. However, in this method, as shown in FIG. 5, it always takes 6 seconds from when the receiving station responds to the 20M frame until it sends the DISIS frame in phase D, so the transmitting station When transmitting multiple images, it is extremely disadvantageous in terms of line cost.

Therefore, the present invention provides data transmission power, which solves the above problems.
The purpose is to present the formula.

[Means for Solving the Problems] In the data transmission system according to the present invention, before transmitting data, the slave station declares its own capabilities to the master station, and the master station proceeds with the transmission procedure based on the information. This is a data transmission method in which data is transmitted by
This feature is characterized in that the master station declares to the slave station that one unit of data transmission has been completed, and in response, the slave station re-declares to the master station the status regarding the previous data transmission and the capabilities of its own station at that time. do.

[Operation] With the above means, the master station can know the latest status of the slave station in addition to the receiving status of the slave station every time one unit of data transmission is completed. Therefore, without requiring special time,
The transmission procedure can proceed without delay.

[Example] Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a transmission control procedure according to an embodiment of the present invention. That is, in phase D after the image transmission is completed, the receiving station transmits a frame expressing the result of the image transmission and a frame expressing the latest state of its own station to the transmitting station. This solves the aforementioned problem. This transmission procedure will be explained in more detail.

FIG. 6 shows the transmission procedure when the receiving station runs out of recording paper during unit-by-unit image transmission. In phase D, the transmitting station transmits MPS frames to the receiving station with the intention of continuous transmission. When the receiving station receives the MPS frame, it transmits the MCF, RTP, or RTN frame and the Dis frame at that time to the transmitting station according to the result of the previous image reception. This DIS frame indicates that there is no reception capability. Therefore, the transmitting station does not continuously transmit images, but immediately enters phase E, transmits a DCN frame, and disconnects the line.

FIG. 7 shows the procedure when the image transmission capability of the receiving station changes after phase C. FIG. 7(1) shows a case where the receiving station does not have the transmission capability in the initial phase B, but acquires the transmission capability at the time of the phase D. In accordance with the information in the DIS frame received in Phase B, the transmitting station regards the receiving station as having no transmission capability and transmits an EOP frame to the receiving station in Phase D with the intention of ending all transmission procedures. In response, the receiving station transmits a frame related to the previous image reception result and a DIS frame indicating the status of its own station at that time to the transmitting station. This DIS frame indicates that it has transmission capability. Based on this information, the transmitting station issues a transmission request to the other station using a DTC frame, and exchanges the transmitting and receiving functions.

FIG. 7(2) shows a case where the receiving station had transmission capability in the initial phase B, but lost the transmission capability in phase D. Based on the information received in Phase B, the transmitting station assumes that the partner station has transmission capability and transmits an EOM frame to poll image information from the partner station. In response, the receiving station transmits a frame related to the previous image reception result and a DIS frame indicating the status of its own station at that time to the transmitting station. This DXS frame indicates that there is no transmission capability. The transmitting station learns from this information that the other station has lost its transmission capability, and transmits a DCN frame to the other station to cut off the line.

FIG. 8 shows a configuration block diagram of an image transmission device for implementing an embodiment of the present invention. 10 is a microprocessor that controls input/output of image data, line connection/cutoff, and execution of transmission procedures; 12 is an image input device that reads a document or digitizes a video signal; 14 is received image data; 16 is a serial/parallel (S/P) converter, 18 is a modem, and 20 is an NCU.

22 is a buffer memory that temporarily stores image data.

Image data from image human power device 12 is sent by microprocessor 10 to S/P converter 16 where it is converted to serial data and sent to modem 18. Modem 18 modulates the serial data from S/P converter 16 or data from microprocessor 10, and the modulated signal is sent via NCU 20 to the telephone line.

The microprocessor 10 connects the HDLC frame to the line.
When outputting data, a signal is output to the line via the S/P converter 16, modem 18, and NCU 20. G
ULF facsimile image data that is not subjected to HDLC framing is sent to the modem 18 and NCU 20.
Outputs a signal to the line via. The same applies when receiving signals from a line.

[Effects of the Invention] As can be easily understood from the explanation of the abnormality, according to the present invention, the status of the receiving side is communicated to the transmitting side again when the transmission of one batch of data is completed, so the transmitting side is always The latest status on the receiving side can be grasped, and image transmission/reception procedures can be carried out without delay.

[Brief explanation of drawings]

Fig. 1 shows the basic transmission procedure of an embodiment of the present invention, Fig. 2 is an explanatory diagram of the transmission procedure phases of CDI facsimile, Fig. 3 shows the HDLC frame format in GIII facsimile, and Fig. 4 shows the GIIr facsimile. The general transmission procedure, Fig. 5 shows the procedure when changing the sending and receiving functions in GIII facsimile, Fig. 6 shows one embodiment of the present invention, Fig. 7 shows another embodiment of the present invention, and Fig. 8 shows the present invention. 1 is a configuration block diagram of an image transmitting/receiving device that implements an embodiment of the invention. FIG. 10: Microprocessor 12: Image input device 14:
Image output device 16: Serial/parallel converter 18
:Modem 20+NCU 22:Buffer memory Figure 1 Time Figure 2 Figure 3 Phase Transmitting station Receiving station Figure 4 Figure 5 Figure 6 Transmitting station Receiving station Transmitting station Receiving station No. 71
figure

Claims (1)

[Claims] This is a data transmission method in which the slave station declares its own capabilities to the master station before transmitting data, and the master station proceeds with the transmission procedure based on that information and transmits the data. One unit of data transmission is Each time the data transmission ends, the master station declares to the slave station that one unit of data transmission has ended, and in response, the slave station re-declares to the master station the status of the previous data transmission and its own capabilities at that point. A data transmission method characterized by: