JPS59167159A - Hdlc data transmitting system - Google Patents

Abstract

PURPOSE:To transmit always data the maximum speed of transmission independently of characteristic of an encoder and a decoder by varying frame length with the data transfer speed and the line speed to transmit the data. CONSTITUTION:A buffer 21 where transmission data is stored, an input task 22 which inputs data to the buffer 21, a transmission task 23 which reads out and outputs data from the buffer 21, and a buffer table 24 which informs the storage state of data in the buffer 21 are provided. The input task 22 inputs data to prescribed areas of the buffer 21 until data indicating that data in the buffer 21 reaches a prescribed quantity or indicating the end of the transmission of the just preceding frame is given from the buffer table 24, and the transmission task 23 reads out data successively from areas, to which the input task 22 completes the data input, and outputs data. With respect to the information of the storage state of data in the buffer 21, it is imformed whether data is stored in the divided areas of the buffer 21 or not, and the number of byte and the start address of data are informed.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This invention relates to high-level data link control procedures (HDL
C) relates to improvements in the HDLC data transmission method for transmitting data.

[Technical background of the invention]

HDLC is a method that divides data of a certain length into multiple parts, adds control codes, error check codes, etc. to each divided part, composes it into one frame, numbers it, and sends it out in units of one frame. However, the transmitting side receives response signals such as RR (receive ready) and RNR (receive not ready) output from the side receiving this frame.

For example, as shown in FIG. 1, numbered data frames 0. Engineering 2. I3, response signal frames RR1,
RR2 and RR3 are returned. Here, the response signal RR indicates that the next frame can be received, and has the number of the next frame expected to be received in the meter.The other response signal RNR indicates that the receiving buffer on the receiving side is It is full and indicates that no more frames can be received continuously.Therefore, the data transmitting side sends a response signal RNR.
When the receiving side receives a response signal RR, it temporarily stops sending the next frame, and then, when the receiving buffer on the receiving side becomes empty, the receiving side sends out a response signal RR to request the sending of the next frame.

Furthermore, in HDLC, the transmitting side can transmit frames up to a predetermined number in advance even if it has not received these response signals. The number of frames that can be sent without waiting for a response in this way is called the maximum number of outstanding frames. However, frames sent without waiting for a response must be held on the transmitting side until the corresponding response signal is returned. Furthermore, the maximum value of the frame length (data amount) that can be sent is set in advance between the transmitting side and the receiving side.

In conventional nuclide transmission methods, when transmitting data, it is better to make the frame length as long as possible to reduce the proportion of additional codes such as control codes and error check codes added to each frame, and as a result, the total transmitted bits can be reduced. Based on the idea that the increase in the number of frames can be minimized and transmission efficiency can be increased, the method is based on the idea that frame transmission is started after the maximum frame length of data is input to the buffer on the transmitting side.By the way, data communication system is configured as shown in FIG. On the transmitting side, data 1 enters encoder 2, and output data 3 of encoder 2 becomes I(DLC
The signal is sent to the transmitting device 4, and from the HDLC transmitting device 4 via the line 5 to the HDLC receiving device 6. The data that has reached the HDLC receiver 6 via the line 5 is output data 7
The data then enters a decoder 8, is decoded, and is output as data 9.

In such a system, when the maximum number of outstanding frames is 2, the quantitative change between data F2 generated when encoding is limited to HDLC transmitter 4 and data F3 output by HDLC transmitter 4 is as follows. , as shown in Figure 3. In this figure, the vertical axis shows the amount of data, the horizontal axis T shows time, K shows the maximum length of the frame, and fti shows the size of each frame sent out.
t0 to t4 indicate the start time of frame transmission, and fo to
f4 indicates each frame to be sent, and Akebono is HDLC
It shows a section in which the output of the transmitting device 4 is stopped.

[Problems with background technology]

As can be seen from FIG. 3, when the amount of data per unit time generated from the encoder 2 is smaller than the output of the HDLC transmitter 4, that is, in the interval from sLX to t3, the line 5 A vacant time tw occurs. This idle time tw causes a decrease in the efficiency of the HDLC communication system when the decoder 8 is connected.

FIG. 4 shows temporal changes in data transfer in a transmission system of the HDLC transmission system to which the decoder 8 is connected, where the vertical axis shows the amount of data and the horizontal axis T shows time.

For the same code (data), the amount of data per unit time generated by the encoder 2 (FIG. 3 Fl) and the amount of data generated by the decoder 8
However, the amount of data input per unit time is the same as the amount of data input per unit time by this decoder 8, and the amount of data input per unit time is represented by 01. G2 indicates the output of encoder 2, G3
indicates the output of the HDLC transmitter 4, G4 indicates the output of the HDLC receiver 6, and twl indicates that the output of the encoder 2 is H.
It shows the idle time of the line 5 that is lost due to the output of the DLC transmitting device 4 decreasing. Due to this idle time tWl, the output of the HDLC receiver 6 is lost as indicated by tA. For this reason, the amount of data per unit time that the decoder 8 accepts is reduced, but since the characteristics of the encoder 2 and decoder 8 are the same, the decoder 8 receives less data. As a result of the encoder 2 continuing to output data even while the data is being taken, data remains in the HDLC receiver f6. Therefore, the HDLC receiving device 6 outputs a response signal 'RNR to inform the HDLC transmitting device f4 to stop outputting data. As a result, the HDLC transmitting device 4 stops outputting, so that an idle time twh occurs at the time 11J5.

However, since the encoder 2 continues to output, the HD
Data remains in the buffer of the LC transmitter 4. Here, as shown in tB, HDL for the output of encoder 2 is
The reception of data by the C transmitter 4 is stopped.

After that, the HDLC receiving device 6 outputs its own accumulated data, returns a response signal RR, and in response,
When the DLC transmitting device 4 outputs its own accumulated data, the data accumulation is resolved and normal data transfer is resumed, but the delay time of data transfer that occurs at this time cannot be recovered.

[Purpose of the invention]

The present invention has been made in view of the drawbacks of the conventional HD LC data transmission method described above, and its purpose is to always transmit at the maximum speed regardless of the characteristics of the encoder and decoder. It is an object of the present invention to provide a more HDLC data transmission method than that for data transmission.

[Summary of the invention]

Therefore, in the present invention, when the data transfer speed output from the encoder is slower than the line speed, the length of the frame to be sent is shortened, and when the data transfer speed is faster than the line speed, the length of the frame to be sent is shortened. Data is transmitted with variable frame length so that the frame length is a predetermined length.

[Embodiments of the invention]

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

FIG. 5 is a block diagram of a transmission system employing the present invention. In the figure, 10 indicates a microprocessor.

A bus 11 extends from the microprocessor 10, and this path 11 includes a memory 12 in which programs and data used by the microprocessor 1 are stored, an encoding unit 13,
The network control unit 14 and HDLC-LS 115 are connected. The encoding unit 13 has a function of encoding data received from the host CPU, the network control unit 14 has functions such as starting and restoring the switching network, and the HDLC-LS 115 has a function of performing HDLC transmission. has. Note that the network control unit 14 uses the signal line 16
By the way, HDLC-LS115 uses R line and T line,
It is connected to a switching network (not shown).

In the transmission system with such a configuration, the microprocessor 1O transmits information to the upper CP according to the program in the memory 12.
The data transmitted from U is received, encoded by the encoding unit 13, and transmitted via the HDLC-LS 115.

Here, a functional block diagram according to the method of the present invention is shown in FIG. In the figure, 21 is a buffer in which transmission data is stored, and an outstanding number (M) of buffer areas MBUF(0) to BUF(M-1) for a predetermined maximum frame length are collected. ing. n is a data manual task which is a means of inputting data to the buffer 21, B is an HDLC transmission task which is a means of reading and outputting data from the buffer 21, and another is a buffer table which is a means of notifying the storage state of data in the buffer 21. be.

Also, data input task B is given data 6,
The data part is output to the buffer 21 as a data part, and the data part is given to the HDLC transmission task B from the buffer 21.
The HDLC transmitter outputs the transmitter path. 4 indicates an interface that connects the data input task n and the buffer table, and 4 indicates an interface that connects the HDLC transmission task and the buffer table.

The above data input task n and HDLC transmission task n operate in parallel, and data input task n
4, the input data δ is stored in the buffer 21. At this time, the data input task n can monitor the operation of each HDLC transmission task using the buffer table. Further, the HDLC transmission task reads data 4 from the buffer 21 while referring to the buffer table, converts it into an HDLC frame, and outputs it as an output data section.

Here, buffer table pickling will be explained.

For each buffer table, as shown in Figure 7, the buffer 21
A register TBL(n) indicating whether each area BUF(n) in the buffer 2177 is empty or has data, and a register TBL(n) for each area BUF(n) in the buffer 2177).
a register ADR8(n) indicating the start address of
It consists of a register B Y T (n) indicating the data cover of each area B U F (n) of the buffer 21 in byte units. When the above register TBL(n)=O, BUF(
n) is empty and ready, TBL(n)
=l indicates that BUF(n) has data and is busy.

First, the operation of HDLC transmission task n will be explained.

The HDLC transmission task has a buffer table (n
), and if TBL(n)=l, buffer 21
From there, data of BYT(n) bytes is read out from the start address ADR8(n), converted into a frame, and sent out. At this time, when a response signal RR (receive ready) is returned from the HDLC receiving device side, the data input task η is made aware of panties ready as an option (n)io. Then, if the number of transmitted frames is within the maximum number of frames that can be sent out, the HDLC transmission task n performs the same processing as above for the area BUF (n+1) next to the sender 210 without waiting for the response signal RR. Perform processing. In this way, the HDLC transmission task performs operations related to data transmission, as in the conventional HDLC transmission system.

Next, the operation of the data input task η will be explained with reference to the flowchart in FIG.

First, it becomes 5TART, and in step 101, an index pointer N for indicating the number of times of processing is set to zero. Next, in step 102, it is determined whether the position (N) is zero or not, and if it is zero, the area B of the buffer 21 is
Assuming that UF(N) is empty, the process proceeds to step 103.

In step 103, the buffer table group BY
By setting zero in T(N) and setting ADR8(N) in address pointer P, it is indicated that the stored data is zero bytes and the area where the upcoming data should be stored is set to "71". Next, in step 104, the data input task η monitors whether the previous frame has been sent by determining whether TBL(N-1) is zero. Here, if YES, the process proceeds to step 105, and it is determined whether data is stored in the area BUF (N) based on whether BYT (N) is zero.

That is, by the flow from step 104 to step 105, it is possible to check whether the data to be sent next has been stored in the area BUF (N), even in some bytes, in response to the sending of the immediately previous frame.

If NO in step 105, proceed to step 110, set TBL(N) to 1, and
Notify the DLC sending task that there is data to send. On the other hand, if the result in step 104 is NO, it means that the previous frame has not been sent.
It is not necessary to notify the DLC sending task n that there is data to be sent, and it is not necessary to notify the DLC sending task n that there is data to be sent.
When it becomes ES, even if the data to be transferred is not stored in the area BUF(N) at least one byte, the process proceeds to the data input operation from step 106 in any case.

In step 106, it is determined whether there is input data δ,
If NO, repeat steps 104 onwards and YES.
If so, proceed to step 107. Stella 7'106 Y
When branching to ES, the input data 25 is stored in the address indicated by the address pointer P in step 107. Furthermore, the process advances to step 108, where the address pointer P is incremented by 1 and BYT(N) is incremented by 1, thereby updating the address in area BUF(N) and displaying the stored data cover. The process then proceeds to step 109, where it is determined whether or not the storage operation has reached a predetermined maximum frame length (pi)K. Here, if the maximum frame length is in bytes (
(if YES in step 109), or the previous frame has been transmitted and the data that can be transmitted is in area B.
If it is stored in UF(N) (proceeding from step 104 to step 105, and NO in step 105), proceed to step 110, and set TBL(N) to 1.
This notifies the HDLC sending task n that there is data to be transferred, and sets the index pointer N to 1.
Increment. Then, the area BI of the buffer 21
In order to process JF(n+1) in the same way, it is determined in step 111 whether the index pointer N has reached the maximum outstanding frame number M, and if the maximum outstanding frame number M has not been reached, the steps are performed from step 102. Repeat up to 110. If the maximum number of outstanding frames M has been reached, the process proceeds to step 101 and the index pointer N
Set to zero and repeat the operations from step 102 onwards.

Here, FIG. 9 shows a change over time in the amount of data transferred according to the method of the present invention. This figure corresponds to FIG. 3 of the conventional example, and the vertical axis indicates the amount of data (bytes), and the horizontal axis T indicates time (seconds).

Also, Fl indicates data generated by the encoder when the HDLC transmitter is disconnected, and F2' indicates data generated by the encoder when the output of the encoder is limited by the HDLC transmitter. , F3' indicate data output by the HDLC transmitter, K indicates the maximum length of the frame, and f indicates the size of each frame to be transmitted. Also s jO~
tn+3 indicates the start point of frame transmission, and fo#f
n+2 indicates each frame sent out.

As is clear from FIG. 9, when the amount of data generated by the encoder per unit time is smaller than the amount of data output by the HDLC transmitter, the frame length of the transmitted frame is shortened.

FIG. 10 shows temporal changes in data transfer in the system of the present invention when a decoder is connected, and corresponds to FIG. 4 of the conventional example. In the figure, the vertical axis indicates the amount of data, and the horizontal axis T indicates time. Furthermore, G1 indicates the amount of data generated by the encoder per unit time (the amount of data that the decoder accepts per unit time), 02' indicates the amount of data output by the encoder, and 03'G4' indicates data output by the HDLC transmitter, and G4' indicates data output by the HDLC receiver.

As is clear from FIG. 10, the idle time of the line that existed in the conventional example shown in FIG. 4 is eliminated, and therefore there is no time left for the HDLC receiver to output data. Therefore, data does not accumulate in the buffer of the HDLC receiving device, and the response signal RNR is not sent back.
Since the HDLC transmitter does not stop outputting, there is no free time tW2 on the line, and there is no time t when the encoder output is not received. That is, the stop time for data input to the decoder and the stop time for data output from the encoder due to the line idle time tw1 + tW2 in the conventional example are eliminated.

〔Effect of the invention〕

As explained above, in the present invention, one frame is separated in two ways: when the maximum frame length is the number of bytes, or when the immediately preceding frame ends its transmission, so that the following effects can be achieved. There is.

In other words, when the amount of data input to the HDLC transmitter per unit time becomes less than the amount of data output by the HDLC transmitter per unit time, the frame length to be sent simply becomes shorter, resulting in idle time on the line. Therefore, the output of the HDLC receiver does not stop.

Also, because of this, the HDLC transmitter does not stop, so data can always be transmitted at the highest possible transmission speed.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing data transmission using the HDLC transmission method,
Figure 2 is a block diagram of the HDLC communication system, Figure 3 is a diagram showing the change in data cover according to the conventional method when the receiving system is not considered, and Figure 4 is a diagram showing the change in data amount according to the conventional method when the receiving system is included. FIG. 5 is a block diagram of the transmission system according to the method of the present invention, FIG. 6 is a functional block diagram of the present invention, FIG. 7 is a block diagram of the main part of FIG. 6, and FIG. 8 is a data input task. FIG. 9 is a diagram showing the change in data amount according to the present invention when the receiving system is not taken into consideration. FIG. 10 is a diagram showing the change in the amount of data according to the present invention when the receiving system is taken into consideration It is a diagram. 2...Encoder 4...HDLC transmitter 6...HDLC receiver 8...Decoder 10...Microprocessor 12...Memory 13...-Encoder 14... Network control unit 15...HDLC-LSI 22...Data input task...HDLC transmission task 21...Buffer chest...Buffer table Agent patent attorney Book 1) Takashi Figure 6 Figure 7

Claims (2)

[Claims] (1) comprising a buffer in which transmission data is stored, means for inputting data into the buffer, means for reading and outputting data from the buffer, and means for notifying the storage state of data in the buffer; The inputting means inputs data into a predetermined area in the buffer until data indicating that the data in the buffer has reached a predetermined amount or that transmission of the immediately preceding frame has been completed is provided from the notifying means. The HDLC data transmission system is characterized in that the outputting means sequentially reads and outputs data from an area where the inputting means has finished inputting data. (2) The means for notifying the storage state of data in the buffer indicates whether data is stored in divided areas in the buffer, the number of bytes of data, and the starting address. HDL described in scope item (1)
C data transmission method.