JP2631699B2 - Cell Formatting Method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] The present invention relates to a cell formatting method for an apparatus which divides information into cells, multiplexes and transmits the information, and aims to provide a cell formatting method which suppresses output of unnecessary information or erroneous information. An information buffer for inputting and outputting information in a first-in first-out manner, wherein the information is divided into cells by reading information in accordance with a write clock corresponding to a valid information identification signal and reading out the information in accordance with a readout clock, and An information length counter for counting,
Read start means for generating a read start signal when the count value of the information length counter reaches a predetermined value or when the end of valid information is detected, and holds the value of the information length counter in response to the read start signal An information length register, a cell counter for counting the read clock in response to the read start signal, and a read clock until the count value of the cell counter matches the value held in the information length register. Read control means for supplying the data to the buffer.

[Industrial applications]

The present invention relates to a cell formatting method in a terminal device that divides information into cells, multiplexes and transmits the information, and particularly relates to a cell formatting method in which output of unnecessary information or erroneous information is suppressed.

In an asynchronous transfer system for the purpose of uniformly handling voice information, image information, and information having different speeds and properties from a data terminal, information is cellized and transmitted.

In this case, it is desired that the cell formatting method for converting information into cells can suppress output of unnecessary information or erroneous information.

[Conventional technology]

FIG. 5 shows the entire configuration of a conventional communication system to which the present invention is applied.
And the signals of the data terminals 13 are cell-multiplexed at the terminal adapter 14 to multiplex the signals into the subscriber line 15 and the subscriber circuit.
1 shows a communication system of an asynchronous transfer system for mutually transmitting data to and from an exchange 17 via 16.

In the terminal adapter 14, the image signal of the audio signal and the video terminal 12 of the audio terminal 11, the encoding / decoding unit 14 ₁
In the converted analog-to-digital (A / D), are divided with the signal of the data terminal 13 to the cell in the cell unit 14 _2, it is multiplexed for each cell in the cell multiplexing / demultiplexing section 14 _3, via the subscriber line 15 The signal is sent to the exchange 17 via the subscriber circuit 16.

On the other hand, multiplexed signal from the exchange 17 is applied to the terminal adapter by reverse path, are separated in the cell in the cell multiplexing / demultiplexing section 14 _3, a digital signal is decomposed cell in the cell unit 14 ₂ restored, the data signals are sent directly to the data terminal 13, the audio signal and an image signal respectively digital-to-analog (D / a) converted by voice terminals 11 in the encoding / decoding unit 14 ₁ is added to the video terminal 12 , As audio and video.

FIG. 6 shows a conventional configuration in the case where cell conversion is performed in the cell conversion section 14. As shown in FIG.

A clock is generated from the terminal clock TCLK and the valid information identification signal ENB via the AND circuit 21, and is applied to the information buffer 22 composed of a FIFO memory as the write clock WE, so that the arriving information is written to the information buffer 22. On the other hand, the information length is counted by adding this clock to the information length counter 23. When the information length comparison circuit 24 detects that the count value of the information length counter 23 has reached a predetermined value, the information length comparison circuit 24 generates an output. The information end detection circuit 25 detects the end of valid information from the valid information identification signal ENB and generates an output. A read start signal is generated from the OR circuit 26 by the generation of any of these outputs, the read start is performed on the read side, and the information length counter 23 is reset to prepare for the counting of the next information length.

The cell counter 27 counts the clock CLK of the cell multiplexing / demultiplexing unit in response to the read start signal, whereby the header timing circuit 28 first generates a cell head signal and outputs it to the cell multiplexing / separating unit. Is generated to control the switching of the selector 29 to output the header information. When the output of the header information is completed, the header timing circuit 28 controls the selector 29 to switch to the information buffer 22 side. The read control unit 30 generates a read clock RE from the clock CLK until the count value of the cell counter 27 reaches a predetermined value.
And information is read from the selector 29 to generate cell information through the selector 29.

When the count value of the cell counter 27 reaches a predetermined value, the read clock RE from the read control unit 30 stops, so that the length of the information part of the cell output from the information buffer 22 becomes the predetermined length. The cell counter 27 stops in this state,
It does not operate until the next read start signal is received.

[Problems to be solved by the invention]

As shown in FIG. 6, in the conventional method, when information is divided into cells, the information length is counted by an information length counter, and the reading side is activated every time a fixed amount of information is accumulated, and the reading is performed in accordance with the counting. The counter on the side counts a predetermined value, reads a certain amount of information from the information buffer, and outputs it as an information part of the cell.

As described above, in the conventional method, the information length read on the reading side is not controlled by the information length counted on the writing side, but simply reads out information of a fixed length. Therefore, unnecessary information is inserted and the reading is performed. Was sometimes heard. Also, if the next information is read before the reading of the last part of the previous information is completed, the head of the next information is read to the last part of the previous information.

The present invention has been made to solve the problem of the related art, and suppresses output of unnecessary information or erroneous information by controlling reading of information from an information buffer using information of an effective information length. It aims to provide a cell formatting scheme.

[Means for solving the problem]

As shown in the embodiment of FIG. 1, the cell formatting method of the present invention comprises a buffer 22 for inputting / outputting information on a first-in first-out basis and by reading information in accordance with a write clock corresponding to valid information and reading / writing in accordance with a read clock. In an apparatus that divides information into cells and outputs the information, an information length counter 23 and read-out activation units 24 and 2 are provided.
5, an information length register 31, a cell counter 27, and read control means 30.

The information length counter 23 counts a write clock corresponding to valid information.

The reading activation means 24 and 25 generate a reading activation signal when the count value of the information length counter 23 reaches a predetermined value or when the end of valid information is detected.

The information length register 31 holds the count value of the information length counter 23 in accordance with the read start signals of the read start units 24 and 25.

The cell counter 27 counts a read clock in response to a read start signal from the read start units 24 and 25.

The read control means 30 supplies a read clock to the buffer 22 until the count value of the cell counter 27 matches the count value of the information length register 31.

[Action]

By writing information to the information buffer that inputs and outputs information on a first-in first-out basis with a write clock corresponding to the valid information, only the valid information is written to the information buffer. On the other hand, the effective information length is counted by counting the write clock by the information length counter.

When the count value of the information length counter reaches a predetermined value or when the end of valid information is detected, a read start signal is generated by the read start unit, and the count value of the information length counter is changed according to the read start signal. The read clock for reading the information buffer is counted by the cell counter in accordance with the read start signal while being held in the length register.

A read clock is supplied to the information buffer until the count value of the cell counter reaches the value held in the information length register, and the information in the information buffer is divided into cells by reading the information in accordance with the read clock. Output.

As described above, in the method of the present invention, the reading of the information from the information buffer is controlled by using the information of the effective information length, so that only the effective information length is output and unnecessary information is prevented from being inserted and output. Even if the writing of the next information is started during the reading of the previous information, the reading is stopped by the end of reading the valid information of the previous information, so that the head of the next information is not erroneously read.

〔Example〕

FIG. 1 shows the configuration of a cell unit in one embodiment of the present invention, in which the same parts as those in the conventional configuration shown in FIG. 6 are indicated by the same reference numerals, and 31 is an information length register.

FIG. 2 is a time chart for explaining the counting of the information length and the writing control in the embodiment of FIG.

When the clock of the information length counter 23 and the write clock WE of the information buffer 22 are generated from the terminal clock TCLK and the valid information identification signal ENB, and the count value of the information length counter 23 reaches a predetermined value (information field length of the cell). The value of the information length counter 23 is written to the information length register 31 via the OR circuit 26 by the output of the information length comparison circuit 24 or the output of the information end detection circuit 25 when the valid information ends, and a read start signal is generated. The reading side is activated, and the information length counter 23 is reset to prepare for counting the next information length.

The cell counter 27 is clocked by the read start signal.
CLK is counted, and the header timing circuit 28 generates a cell head signal, controls the selector 29 by generating a header timing signal, and uses the header information and the value of the information length register 31 as cell information. First, output. When the output of the header information is completed, the header timing circuit 28 controls the selector 29 to switch to the information buffer 22 side. Further, the read control unit 30 outputs the clock CLK.
, A read clock RE is generated, whereby information is read from the information buffer 22 and cellized information is generated via the selector 29.

When the information length held in the information length register 31 matches the count value of the cell counter 27, the read clock RE output from the read control unit 30 stops, and the information buffer 22
Stops outputting information from. Therefore, it is possible to prevent the information buffer from outputting only the information having the effective information length and inserting unnecessary information to be transmitted. After counting to a certain value, the cell counter 27 stops counting until the next read start signal is generated.

FIG. 3 shows a specific configuration example of the read control unit 30 in the embodiment shown in FIG. 1, in which the same parts as those in FIG. ~
44 is an AND circuit, 45 is a flip-flop (FF), 46 is an OR circuit, and 47 is a decode circuit.

FIG. 4 is a time chart showing signals of respective parts in the circuit of FIG.

The cell counter 27 starts counting upon receiving the read start signal. First, the header timing circuit 28 generates a header timing signal to perform switching control in the selector 29 to output the header information and the value of the information length register 31, and to suppress reading of information from the information buffer 22 during this time. Since the coincidence output of the comparison circuit 41 is “1” and the FF 45 is set via the OR circuit 46 and the AND circuit 42 to output “1”,
When the header timing signal stops and the header information is output, the read enable signal RDENB is output and the AND circuit
The read clock RE is output via 44 and the information buffer 22
, Information is read from the.

When the count value of the cell counter 27 matches the information length of the information length register 31 in the comparison circuit 41, the coincidence output becomes “0”.
FF45 is reset and the read enable signal RDEN
Since B stops and the read clock RE is not output, the information read from the information buffer 22 ends. The cell counter 27 stops when it counts up to a value corresponding to the length of the information portion of the cell, and does not operate until the next read start signal is received.

In FIG. 4, (a) shows the operation when the effective information length is equal to the length (12) of the information portion of the cell, and (b) shows the operation when the effective information length is shorter than the length of the information portion of the cell (6). The operation in a certain case is shown.

〔The invention's effect〕

As described above, according to the present invention, in the cell formatting method in which information written in an information buffer is read and divided into cells, reading of information from the information buffer is controlled using information of an effective information length. As a result, it is possible to suppress output of only the effective information length and unnecessary information being inserted and output, and even if writing of the next information is started during reading of the previous information, the effective information of the previous information is not included. Since reading stops when reading ends,
There is no mistake in reading the beginning of the next information.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a cell unit in one embodiment of the present invention, FIG. 2 is a time chart for explaining counting of information length and write control in the embodiment of FIG. 1, and FIG. FIG. 1 is a diagram showing a specific configuration example of a read control unit in the embodiment of FIG. 1, FIG. 4 is a time chart showing signals of each unit in the circuit of FIG. 3, and FIG. 5 is a conventional communication system to which the present invention is applied. FIG. 6 is a diagram showing a configuration of a conventional cell forming unit. 11 Voice terminal 12 Image terminal 13 Data terminal 14 Terminal adapter 15 Subscriber line 16 Subscriber circuit 17 Exchange 22 Information buffer 23 Information length counter 24 … Information length comparison circuit 25 …… information end detection circuit 27 …… cell counter 28 …… header timing circuit 29 …… selector 30 …… readout control unit 31 …… information length register

Continuation of the front page (56) References JP-A-1-175433 (JP, A) JP-A-62-142446 (JP, A)

Claims (1)

(57) [Claims] An apparatus for dividing information into cells and outputting the information, wherein a buffer for inputting and outputting information in a first-in first-out manner (22)
And valid information only by the valid information identification signal in the buffer (2
2) a write clock generating means (21) for generating a clock for writing to, and an information length counter (23) for counting the write clock
Read start means (24, 25) for generating a read start signal when the count value of the information length counter (23) reaches a predetermined value or when the end of valid information is detected; An information length register (31) for holding the value of the information length counter (23), a cell counter (27) for counting a read clock in response to the read start signal, and a cell counter (27). A read control unit (30) for supplying a read clock to the buffer (22) until the count value matches the value held in the information length register (31) suppresses output of unnecessary information or erroneous information. A cell formatting method.