JPH06188942A - Data communication equipment - Google Patents

Abstract

PURPOSE:To cope with the transmission request of a monitor frame in real time by using an HDLC control means which enqueues the transmission request of the monitor frame into a transmission queue in a priority level higher than those of information transfer frames in the transmission queue at the time of issue of this transmission request. CONSTITUTION:After a data link is set at the information transfer phase, I- frames 6 and 7 are transmitted from a terminal B to a terminal A. At this time, the frame 6 brings about a CRC error by a line noise or the like, but the frame 7 is normally accepted by the terminal A. The terminal A generates a REJ frame as an S frame for the retransmission request for the purpose of requesting retransmission of the frame 6. Since the S-frame is enqueued into the transmission queue in the high priority level, it is connected before other I-frames and is first transmitted to a line, and I-frames are transmitted thereafter. Therefore, the terminal B immediately retransmits the I-frame 6 when accepting REJ from the terminal A, and the quick retransmission processing is performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data communication device, and more particularly, to an HDLC (High level Da).
The present invention can be applied to a data transmission method using a ta Link Control) control procedure, as well as a G4 facsimile LAPB (Link Access Process).
Dure Balanced) procedure and ISDN (Int
integrated Services Digital
Network terminal's LAPD (Link Acce)
ss Procedure on the Dchan
data communication device that can be applied to the S. frame and the like, and in particular, can shorten the time until an S frame (Supervision frame) is sent and quickly perform the operation of the partner station with respect to the S frame. Regarding

[0002]

2. Description of the Related Art Conventionally, there is a communication control device reported in, for example, Japanese Unexamined Patent Application Publication No. Hei 2-161856. Here, by arranging transmission data to be aborted when a memory read error occurs, It has an advantage that it is possible to prevent erroneous data from being transmitted.

Also, conventionally, N having a chaining function has been used.
Regarding the busy signal transmission method in the O7 signal device,
For example, there is the one reported in Japanese Patent Laid-Open No. 2-46059, in which the busy signal generator is driven when the next frame request is issued to the memory controller after the busy transmission instruction is given from the host. With this configuration, even if the device itself becomes busy while sending a long frame, there is an advantage that the busy signal can be sent without interrupting the frame.

[0004]

However, in the conventional data communication apparatus as described above, the priority of the transmission queue is not manipulated, and therefore, a plurality of I's are added to the transmission queue.
Frame (Information transfer)
(frame: information transfer frame), when an S frame transmission request is generated in a state where the S frame is transmitted, it takes time until the S frame is actually transmitted. Therefore, the operation of the partner station for this S frame The problem itself was that it lacked speed. Also, during transmission of an I frame, a U frame (Unnumbered fr
(ame: unnumbered frame) transmission request occurs,
Since waiting for the end of the transmission of the I frame, there remains a problem that the processing of disconnecting and resetting the data link is delayed.

Further, conventionally, when an I frame is being transmitted and a retransmission request or a busy notification S frame is received, the transmission of the retransmission I frame, I
There was a problem that the process of stopping frame transmission was delayed. Also, when an I frame is being transmitted and a busy notification S frame is being received, the transmission of the frame has been waited for or aborted. In some cases, the I frame being transmitted may be valid. Therefore, there remains a problem that efficient I-frame transmission and quick busy processing are difficult to perform.

Here, the above-mentioned S frame, U frame and I frame will be specifically described. Generally, the S frame / U frame has a short frame length, while the I frame has a long frame length. When the application is a G4 facsimile, the S frame is 2 bytes, the U frame is 2 to 5 bytes, and the I frame is 2048 bytes at maximum in the standard mode. Further, the maximum number k of outstanding I frames (the maximum value of the number of I frames that can be continuously transmitted without confirmation from the other party) is 7.
The S frame is used for confirmation / retransmission request for the command of the partner station and the busy notification of the own station, and the U frame is
The I frame is used for setting and disconnecting the data link, and the I frame is used for transferring the upper data frame. I
The frame transmission time depends on the data transmission rate, but ISD
It becomes 64 kb / s in B-ch of N basic I / F, and 2
It takes about 250 msec to transfer 048 bytes, and it takes 1.75 sec for 7 frames. The HDLC frame is transmitted / received in synchronization with the flag (01111110), and the abort is realized by sending consecutive "1" s (... 11111111 ...) Of 7 bits or more.

Therefore, the present invention makes it possible to shorten the time until the S frame is transmitted to speed up the operation of the partner station with respect to the S frame, and disconnect the data link without wasteful transmission of the I frame. Data for which processing and resetting processing can be quickly performed, and further, retransmission processing and busy processing can be quickly performed without wasteful I frame transmission, and efficient I frame transmission can be performed. It is intended to provide a communication device.

[0008]

The invention according to claim 1 is
When a request to send a monitoring frame (S frame: Supervision frame) is made in a state where a plurality of data frames are connected to a transmission queue for data frame transmission, this is sent to an information transfer frame (I frame Information) in the transmission queue. transfer
HDLC (High level Data L) that performs processing to connect to the transmission queue with a higher priority than r frame)
The present invention is characterized by having a data transmission means using an ink control) control procedure.

According to a second aspect of the present invention, in the invention of the first aspect, an unnumbered frame (U frame: Un
HDL that aborts the unnumbered frame that is being transmitted when there is a request to transmit the numbered frame)
It is characterized by having a data transmission means using the C control procedure. The invention according to claim 3 is the invention according to any one of claims 1 and 2, further comprising a data transmission means using an HDLC control procedure for aborting an information transfer frame being transmitted when a supervisory frame for a retransmission request and a busy notification is received. It is characterized by that.

The invention according to claim 4 has the function of recognizing the number of untransmitted bytes of the information transfer frame frame which is being transmitted in the invention according to any one of claims 1 to 3, and when the busy notification supervisory frame is received, HDLC that chooses to abort only when the number of unsent bytes is more than a preset value
It is characterized by having a data transmission means using a control procedure.

[0011]

According to the first aspect of the present invention, when a plurality of data frames are connected to the transmission queue for data frame transmission and an S frame transmission request is issued, this is transmitted from the I frame in the transmission queue. It is possible to perform data transmission using the HDLC control procedure that performs processing of connecting to the transmission queue with high priority. Therefore, even if I frames remain in the transmission queue, the S frame can be preferentially transmitted, so that the time until the S frame is transmitted can be shortened and the operation of the partner station for the S frame can be reduced. Can be quick. Therefore, for changes in state,
More real-time response is possible.

According to the second aspect of the invention, when a U frame transmission request is issued, data transmission can be performed using the HDLC control procedure for aborting the I frame being transmitted. Therefore, if there is a U frame transmission request,
Even if the I frame is being sent, the U frame can be sent by aborting the I frame, so that the data link disconnection process and the resetting process can be quickly performed without wasteful I frame transmission.

According to the third aspect of the invention, it is possible to perform data transmission using the HDLC control procedure for aborting the I frame that is being transmitted when the S frame of the retransmission request and the busy notification is received. Therefore, S for resend request and busy notification
Since it is possible to abort an I frame even when it is being sent at the time of receiving a frame, it is possible to perform a quick retransmitting process and a busy process without wasteful I frame sending.

According to the fourth aspect of the present invention, the number of untransmitted bytes of the I frame being transmitted is recognized, and it is selected to abort only when the number of untransmitted bytes is larger than a predetermined set value when the busy notification S frame is received. Data transfer can be performed using the HDLC control procedure. Therefore, at the time of receiving the S frame of the busy notification, it is possible to determine whether or not to abort the I frame depending on the number of untransmitted bytes even when the I frame is being transmitted. Busy processing can be performed.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration when applied to a G4 facsimile according to each embodiment of the present invention. Figure 1
In FIG. 1, 1 is a system control unit, 2 is an image storage unit that stores image data to be transmitted / received, 3 is an encoding / decoding unit that performs encoding / decoding of transmission / reception data, and 4 is communication control It is a communication control unit. Next, 5 and 6 are an input unit and an output unit, respectively, 7 is an operation unit for managing the operating condition and operation condition of the facsimile, and 8 is a time measuring unit for managing the time. Next, 9 is an S frame control unit that controls an S frame used to perform confirmation / retransmission request for a command from the partner station or busy communication of the own station, and 10 is a data link setting or disconnection. Is a U frame control unit that controls a U frame used to perform the above, and 11 is an I frame control unit that controls an I frame used to transfer a higher-order data frame.
2 and 13 are a communication memory and an upper layer control unit, respectively.
Reference numeral 14 is an HDLC communication LSI that performs HDLC framing function, 0 insertion / deletion function, FCS addition / analysis function, and the like, and 15 controls the communication LSI, controls transmission / reception of each frame, and transmits the transmission frame. A frame transmission / reception control unit that manages the number of untransmitted frames and controls the transmission queue, and 16 is a LAPB (CCITT Recommendation X.7) defined as a layer 2 protocol of G4 facsimile.
5, X. 25, T. 90) LAP controlling the protocol
The B control unit.

(Embodiment 1) FIG. 2 is a diagram showing an example of a retransmission request according to an embodiment of claim 1 of the present invention, and FIG. 3 is an operation according to an embodiment of claim 1 of the present invention. It is a flowchart which shows a flow. This embodiment is a case where it is applied to the G4 facsimile of FIG. First, as shown in FIG. 2, after the data link is set and the information transfer phase is set,
From the terminal B, the I frames (6) and (7) are transmitted to the terminal A. At this time, the I frame (6) has a CRC error due to line noise or the like, and the I frame (7) is normally accepted by the terminal A. Since the terminal A makes a retransmission request for the I frame (6), it is an S frame R that makes a retransmission request.
Generate an EJ frame. At this time, in the terminal A, I frames (0) to (5) waiting to be transmitted are present in the transmission queue. This transmission queue is composed of a FIFO. In this embodiment, since the S frame is connected to the transmission queue with a high priority, it is connected before other I frames, transmitted first to the line, and the I frame is transmitted subsequently. For this reason, when the terminal B receives the REJ from the terminal A, the terminal I can immediately retransmit the I frame (5), and can quickly perform the retransmission processing. When terminal A is busy, R
By transmitting the NR frame with priority, careless transmission of the I frame from the terminal B can be prevented.

Next, the operation flow of this embodiment will be described with reference to the flowchart of FIG. First, if there is an S frame transmission request, it is determined whether or not there is an I frame in the transmission queue (process S ₁ ). If there is an I frame in the transmission queue, the S frame is connected before the I frame (process S ₁ ). ₂ ) On the other hand, if there is no I frame in the transmission queue, the S frame is connected to the end of the transmission queue (process S ₃ ).

As described above, in the present embodiment, when a plurality of data frames are connected to the transmission queue for data frame transmission and an S frame transmission request is made, this is sent to the I frame in the transmission queue. It is possible to perform data transmission using the HDLC control procedure for performing the process of connecting to the transmission queue with higher priority. Therefore, even if I frames remain in the transmission queue, the S frame can be preferentially transmitted, so that the time until the S frame is transmitted can be shortened and the operation of the partner station for the S frame can be reduced. Can be quick. Therefore, it is possible to respond to a change in state in more real time.

(Embodiment 2) FIG. 4 is a diagram showing a link disconnection request example according to an embodiment of claim 2 of the present invention and a link disconnection request example of a comparative example, and FIG. 3 is a flowchart showing an operation flow according to an embodiment of No. 2;
Here, the upper part of FIG. 4 is the comparative example, and the lower part of FIG. 4 is the present embodiment. This embodiment is a case where it is applied to the G4 facsimile of FIG.

First, as shown in FIGS. 4 and 5, after the data link is set and the information transfer phase is entered, an error occurs in the upper layer in the terminal A and a data link disconnection request comes (process S ₁₁ ). . At this time, if the I frame is being transmitted (process S ₁₂ ), it is aborted (process S ₁₃ ), and a frame DISC for making a disconnection request is generated and transmitted (process S ₁₄ ). On the other hand, receiving the confirmation frame UA, the link is disconnected.

As described above, in this embodiment, when a U frame transmission request is issued, data transmission can be performed using the HDLC control procedure for aborting the I frame being transmitted. Therefore, if there is a U frame transmission request,
Even if the I frame is being sent, the U frame can be sent by aborting the I frame, so that the data link disconnection process and the resetting process can be quickly performed without wasteful I frame transmission.

(Embodiment 3) FIG. 6 is a diagram showing an I frame retransmission example according to an embodiment of claim 3 of the present invention and an I frame retransmission example of a comparative example. Here, the upper part of FIG. 6 is a comparative example, and the lower part of FIG. 6 is the present embodiment. This embodiment is a case where it is applied to the G4 facsimile of FIG. First, as shown in FIG. 6, after the data link is set and the information transfer phase is entered, the terminal B recognizes the lack of the I frame from the terminal A and sends out the REJ of the retransmission request. Then terminal A
Then, REJ is recognized, and if an I frame is being sent at that time, it is aborted and a retransmitted I frame is sent. For this reason, careless transmission of the I frame can be prevented, and quick resend processing can be performed. When the busy notification frame RNR is received from the terminal B, the load on the terminal B is eliminated by aborting the transmission frame, and the terminal A can immediately send another frame.

As described above, in this embodiment, data transmission can be performed using the HDLC control procedure for aborting the I frame that is being transmitted when the S frame for the retransmission request and the busy notification is received. Therefore, S for resend request and busy notification
Since it is possible to abort an I frame even when it is being sent at the time of receiving a frame, it is possible to perform a quick retransmitting process and a busy process without wasteful I frame sending.

(Embodiment 4) FIG. 7 is a diagram showing an example of recognition of the number of untransmitted bytes according to an embodiment of claim 4 of the present invention.
FIG. 8 is a flow chart showing an operation flow according to an embodiment of claim 4 of the present invention. This embodiment uses G4 of FIG.
This is the case when applied to a facsimile. First, as shown in FIGS. 7 and 8, after the data link is set and the information transfer phase is entered, the terminal B becomes busy due to lack of memory and sends out an RNR for busy notification. Next, the terminal A recognizes the RNR, and if the I frame is being transmitted at that time (process S ₂₁ ), the number of untransmitted bytes at that time is confirmed, and the number of untransmitted bytes> predetermined set value (basically If it is a small value) (process S ₂₂ ), I
Abort without frame sending (processing S _23), to retransmission processing and busy (processing S _25). On the other hand, if the number of untransmitted bytes ≦ a predetermined setting value (process S ₂₂ ), the I being transmitted is transmitted.
The transmission of the frame is completed (process S ₂₄ ), and the retransmission process and the busy process are performed (process S ₂₅ ). The terminal B can receive this I frame depending on the case, and even if it cannot be received, the number of bytes transmitted without being aborted is a small value, so that the time effect is small. Therefore, efficient I frame transmission can be performed at the timing when the busy notification is received.

In this way, in this embodiment, the number of untransmitted bytes of the frame being transmitted is recognized, and when the number of untransmitted bytes of the busy notification S frame is received is larger than a predetermined set value, abort is selected. Data transmission using the HDLC control procedure can be performed. For this reason, when the busy notification S frame is received, it is possible to determine whether or not to abort the I frame depending on the number of untransmitted bytes even when the I frame is being sent. Busy processing can be performed.

[0026]

According to the present invention, the time until the S frame is transmitted can be shortened to speed up the operation of the partner station with respect to the S frame, and data can be transmitted without wasteful I frame transmission. The link disconnection process and the reconfiguration process can be quickly performed, and the retransmission process and the busy process can be quickly performed without wasteful I frame transmission, and more efficient frame transmission can be performed. The effect is that you can do it.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration when applied to a G4 facsimile according to each embodiment of the present invention.

FIG. 2 is a diagram showing an example of a retransmission request according to an embodiment of claim 1 of the present invention.

FIG. 3 is a flowchart showing an operation flow according to an embodiment of claim 1 of the present invention.

FIG. 4 is a diagram showing a link disconnection request example according to an embodiment of claim 2 of the present invention and a link disconnection request example of a comparative example.

FIG. 5 is a flowchart showing an operation flow according to an embodiment of claim 2 of the present invention.

FIG. 6 is a diagram showing an I frame retransmission example according to an embodiment of claim 3 of the present invention and an I frame retransmission example of a comparative example.

FIG. 7 is a diagram showing an example of recognizing the number of untransmitted bytes according to an embodiment of claim 4 of the present invention.

FIG. 8 is a flowchart showing an operation flow according to an embodiment of claim 4 of the present invention.

[Explanation of symbols]

 1 system control unit 2 image storage unit 3 encoding / decoding unit 4 communication control unit 5 input unit 6 output unit 7 operation unit 8 timekeeping unit 9 S frame control unit 10 U frame control unit 11 I frame control unit 12 communication memory 13 Upper layer control unit 14 HDLC communication LSI 15 Frame transmission / reception control unit 16 LAPB control unit

Claims (4)

[Claims] 1. A monitoring frame (S frame: Supervision frame) in a state where a plurality of data frames are connected to a transmission queue for transmitting data frames.
Of the information transfer frame (I frame: Information t) in the transmission queue.
HDLC (High level) that performs processing to connect to the transmission queue with a higher priority than transfer frame (transfer frame)
l Data Link Control) A data communication device having a data transmission means using a control procedure. 2. An unnumbered frame (U frame: Unnu)
If there is a request to send a (framed frame),
2. The data communication device according to claim 1, further comprising a data transmission unit using an HDLC control procedure for aborting the unnumbered frame being transmitted. 3. An HD for aborting the information transfer frame being transmitted when a resend request and a busy notification supervisory frame are received.
3. The data communication device according to claim 1, further comprising a data transmission unit using an LC control procedure. 4. Having a function of recognizing the number of untransmitted bytes of an information transfer frame being transmitted, and selecting to abort only when the number of untransmitted bytes is greater than a predetermined set value when a busy notification monitoring frame is received. 4. A data transmission means using the HDLC control procedure according to claim 1,
The described data communication device.