JP2002198963A - Band generation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the number of flip-flops required for the configuration of a band generation device, in order to decrease the circuit scale and the power consumption. SOLUTION: The band generation device is equipped with an output timing counter 502, which counts the output timing of a corresponding cell for each channel and responds to the channel number, and counter initiation means 506-510, which generate initiation signals for starting the count by each output timing counter and respond to the output timing counter. Each counter initiation means is configured to output the initiation signals when signals indicating that there is a corresponding input cell are inputted and cell output timing signals generated at a transmission path interface unit of physical layers are inputted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a band generating device of an ATM traffic shaping device for generating a rate at which an input cell is output to a communication network when the cell is output.

[0002]

2. Description of the Related Art In ATM transmission, regarding the transmission of a fixed-length data packet called a cell from a terminal device onto a transmission line called a network, the transmission band of the transmission line, that is, the transmission interval of cells from the terminal ( This is called a cell rate.) Is defined based on the contract. Since cells transmitted at intervals shorter than the transmission interval specified in the contract are discarded to avoid collision with cells from other terminals, as shown in FIG. , Traffic shaping device 10
2, the transmission interval of the cell 104 from the cell generation unit 106 is adjusted to an interval suitable for the contract band.

FIG. 2 shows a conventional A in an ATM terminal device.
3 shows an output circuit configuration of a TM cell. In the figure, a traffic shaping device 102 receives cell data from a data generation side, and generates a cell output timing according to a contracted cell rate. The data that has been traffic-shaped by the traffic shaping device 102 is written to the FIFO memory 200 of the physical layer via a UTOPIA (a rule defined by the ATM Forum on the transfer of cell data between the ATM layer and the physical layer) interface.

[0004] In the physical layer, the cell data stored in the FIFO memory 200 is read by the read frame generation control unit 20.
The cell is read out according to the cell timing signal from 2 and the cell is incorporated into the frame of the transmission line by the frame generation unit 204 and the data is transmitted to the transmission line.

FIG. 3 shows the overall configuration of a traffic shaping device having a conventional configuration. In the traffic shaping device 300, when cells transmitted from the cell generation unit (106 in FIG. 1) of the ATM terminal device are interfaced in the cell input I / F 302, each cell is identified by its identification unit in each channel (# 1). , # 2, ...,
#N) and stored in the cell buffer 304 prepared for each. After that, the cell input I / F 302 sends the cell identification result for each channel to the band generation unit 306 as a cell input signal, where the cell output timing is generated by band generation control according to each cell. Since the timing generation in the band generation unit 306 is performed in parallel for each channel, the cell output timing may occur at the same time. After the arbitration is performed in the contention control unit 308, the cell output instruction is sent to the cell output unit. It is provided to the I / F 310. The cell output I / F 310 is
Based on an output instruction from the contention control unit 308, the cell of the target channel is read from the cell buffer 304 and output to the physical layer.

FIG. 4 is a block diagram of a conventional band generation unit in the traffic shaping device. The band generator 306 includes a plurality of output timing generators 400a, 400b,. . . ,
400n. Each output timing generation unit 400
An m-bit output timing counter 402 for counting the output timing of a cell, an m-bit decoder 404 for outputting a cell output signal, and the output timing counter 4
An input cell counter 406 and a decoder 408 are provided as counter activating means for activating the 02.

When a cell input signal indicating that a cell of a corresponding channel has been input is input to the traffic shaping device, the input cell counter 406 counts up by one and its output becomes 1. Decoder 40
Reference numeral 8 denotes a decoder that outputs “High” when the output of the input cell counter 406 is other than 0. Therefore, when “1” is output from the input cell counter 406, the decoder 408 outputs “High”. Becomes The “High” signal of the decoder 408 is output from the output timing counter 40.
2 is input to the CE (clock enable) terminal,
Output timing counter 402 starts its counting operation according to the clock signal.

[0008] A decode value is set in the decoder 408 in accordance with a band to be set in advance. When the output value of the output timing counter 402 matches the value of the decoder 408, a cell output signal from the decoder 408 is output. It is output. This output is also input to the input cell counter 406, whereby the counter value is decremented by one.
When the count value of the input cell counter 406 becomes 0, the output timing counter 402 stops counting,
It becomes an idle state. While the cell output signal is output,
When the cell input signal is continuously input to the input cell counter 406, the value of the input cell counter 406 becomes 0,
That is, the output timing counter 402 continues to operate until there is no cell output request. As described above, the band generation unit 306 transmits the cell output signal at intervals according to the band contracted with the network side.

[0009]

However, in the conventional band generator 306, the output timing counter 40 provided for each output timing generator 400 is provided.
The output timing counted by 2 must be designed to be able to count the decode value corresponding to each band in consideration of the transmission interval corresponding to the bit length (53 bits) of the cell. And the current consumption of the flip-flop (FF) is large.

When a conventional traffic shaping device is employed in an ATM terminal device, a FIFO memory for temporarily storing cells after traffic shaping is required on the physical side of the UTOPIA interface, which is a circuit of the entire device. With an increase in scale and an increase in delay time until data transmission to a transmission path, data transmission that requires real-time performance is insufficient.

Accordingly, it is an object of the present invention to provide a band generating apparatus capable of reducing the number of flip-flops required for the output timing counter.

It is another object of the present invention to provide a band generating apparatus capable of eliminating the need for a FIFO memory for storing cells on the physical layer side of an ATM terminal device.

[0013]

In order to achieve the above object, the present invention relates to a band generating apparatus of an ATM traffic shaping apparatus for generating a rate at which an input cell is output to a communication network when the cell is output. An output timing counter corresponding to the number of channels for counting the output timing of a corresponding cell for each channel, and a counter activation corresponding to the output timing counter for generating an activation signal for starting the counting by the output timing counters Means, wherein each counter activation means, when a signal indicating that there is a corresponding input cell is input, and when an output timing signal of the cell is input, the counter activation means for outputting the activation signal, It is comprised including.

In this case, each of the counter activating means includes an input cell counter for counting the number of corresponding cells in the ATM traffic shaping device, and the presence or absence of the corresponding input cell according to the output of the input cell counter. And a decoder that outputs a signal indicating that there is a corresponding input cell from the decoder, and outputs a start signal of the output timing counter when an output timing signal of the cell is input. It is preferable to include a logic circuit.

Here, the output timing signal of the cell provided to each of the counter starting means is preferably an output timing signal of the cell generated by the transmission line interface of the physical layer.

Further, the band generating apparatus according to the present invention may further include a 6-bit counter for generating an output timing signal of a cell supplied to each of the counter starting means.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on one illustrated embodiment. FIG. 5 is a block diagram illustrating a configuration of the band generation device according to the first embodiment of the present invention. The band generator includes a plurality of output timing generators 500a, 500b,. . . , 5
00n. Then, each output timing generation unit 50
0 is an output timing counter 502 for counting the output timing of the cell, a decoder 504 for outputting a cell output signal, an input cell counter 506 as a counter activation means for activating the output timing counter 502,
A decoder 508 and an AND operation circuit 510 are provided.

The output timing counter 502 is a predetermined bit counter which starts counting in response to a start signal from a logical product operation circuit 510 described later.
Until the cell output signal from 04 is input to its reset terminal, it is counted up in synchronization with the clock signal. The output timing counter 502 used in the present invention can be constituted by a flip-flop circuit similarly to the conventional one. However, when the conventional output timing counter has m bits, the output timing counter 502 becomes m−5. It can be composed of bits. This will be described later.

As in the conventional configuration, a decode value is set in the decoder 504 in accordance with a band to be set in advance. If the counter value of the output timing counter 502 matches the decode value set here, the cell Is output.

Input cell counter 506 and decoder 50
As 8, the same as the conventional configuration is used. That is, the input cell counter 506 counts the number of cells stored in the cell buffer of the traffic shaping device, and counts up when receiving a cell input signal and counts down when receiving a cell output signal from the decoder 504. . The decoder 508 outputs “High” when the count value of the input cell counter 506 is other than zero, and outputs “Low” when the count value is zero.

When both of the two input signals are at the “High” level, the logical product operation circuit 510 outputs “High” as a start signal and supplies it to the CE terminal of the output timing counter 502. Here, one input signal of the AND operation circuit 510 is an output signal of the decoder 508, and the other input signal is a signal synchronized with the output timing of the cell (hereinafter, referred to as a cell timing signal). In this embodiment, the cell timing signal is a cell output timing signal (pulse with a 53-bit interval corresponding to the data length of the cell) generated by the transmission line interface unit of the physical layer. The other output timing generator 50
A common cell timing signal from the physical layer is also input to 0b to 500n. Therefore, the logical product operation circuit 510 is
Only when the decoder 508 is outputting a “High” signal indicating that there is a cell in the cell buffer, and when a cell timing signal from the physical layer is input (ie, transitions to a “High” level) , And outputs a start signal of the output timing counter 502. As a result, the output timing counter 502 starts counting up only at the output timing of the cell, and does not start counting up immediately if a cell is input but does not match the output timing of the cell. .

Next, the operation of the band generator will be described. When a cell input signal indicating that a cell of the corresponding channel has been input is input to the traffic shaping device, the input cell counter 506 counts up by one and its output becomes 1. Decoder 5
08 outputs “High” when 1 is output from the input cell counter 506. Here, when the cell timing signal from the physical layer is input to the logical product operation circuit 510 and becomes a “High” level, the activation signal becomes “High”.
Is input to the CE terminal of the output timing counter 502, and the output timing counter 502 starts its counting operation according to the clock signal.

When the output timing counter 502 counts up and matches the set value of the decoder 508, a cell output signal is output from the decoder 508. This output is also input to the input cell counter 506, whereby the counter value is decremented by one. When the count value of the input cell counter 506 becomes 0, the output timing counter 502 stops counting and enters an idle state. When the cell input signal is continuously input to the input cell counter 506 while the cell output signal is output, the logical product operation circuit 510 outputs the next cell output timing (input of the next cell timing signal). , The output timing counter 502 is started. Then, the output timing counter 502 keeps operating at the cell timing interval until the value of the input cell counter 506 becomes 0, that is, until there is no cell output request. In this way, the band generation device according to the above-described embodiment transmits the cell output signal at intervals according to the band contracted with the network side.

As described above, in the above embodiment,
The output timing counter 502 of each of the output timing generation units 500a to 500n starts counting up in synchronization with a common cell timing signal from the physical layer.
Therefore, it is not necessary for each output timing counter 502 to count in consideration of the bit length of the cell, and the bit length of the counter can be reduced as compared with the conventional configuration. That is, 5 bits can be reduced compared to the conventional output timing counter (the cell timing signal is a pulse for every 53 bits and is smaller than 63 (26) which can be counted with 6 bits, so that 5 bits can be reduced). Therefore, when the conventional output timing counter has m bits, the output timing counter according to the present embodiment can be configured with m-5. As a result, assuming that the number of channels is n, the number of flip-flops for 5n bits can be reduced for the output timing counter. This can be expected to have a sufficient reduction effect even if the number of flip-flops 2n increased by the AND operation circuit 510 is considered.

FIG. 6 shows an example of the configuration of a traffic shaping device when the band generating device according to the embodiment is employed. Here, the function of each component is the same as that in the conventional art, and the description thereof is omitted here. As shown in the figure, when the band generation device 606 according to the present embodiment is adopted, a cell timing signal from the physical layer is provided here. A common cell timing signal is also supplied to the contention control unit 608 and the cell output I / F 610, and these are operated in synchronization with this signal.

FIG. 7 shows an output circuit configuration of an ATM cell when the band generating device according to the above embodiment is employed. As described above, in the band generation device according to the present invention, cells are transmitted from the traffic shaping device 702 in synchronization with the cell timing signal from the frame generation control unit 700 in the physical layer. The cell data after shaping can be directly output to the frame generation unit 704 without the need for the FIFO memory for absorbing the asynchronous input / output timing required in the conventional configuration. The traffic shaping device 702 includes a frame generation control unit 700
A signal indicating the presence or absence of an output cell. This is to make the frame generation unit 704 insert an empty cell, which is an invalid cell, on the transmission path side when there is no cell transmitted from the traffic shaping device 702.

FIG. 8 is a block diagram showing the configuration of the band generating device according to the second embodiment of the present invention. In the description of this embodiment, the same components as those in the previous embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In this embodiment, the band generation device 800
Is, in addition to the configuration of the band generation device of the previous embodiment,
A set of 6-bit counters 802 and a cell interval decoder 804 are provided for generating a cell timing signal therein. That is, the counter 802 is always started in synchronization with the clock signal, and supplies the count value to the cell interval decoder 804. Cell interval decoder 804
, The bit length of the 53-bit cell is set in advance, and when the counter value of the counter 802 matches this,
Outputs a cell timing signal. This cell timing signal is supplied to the AND operation circuit 510 of each of the output timing generation units 500a to 500n, as in the case of the previous embodiment, and each output timing counter 502 is started based on this. .

[0029]

As described above, according to the present invention, it is possible to reduce the number of flip-flops required for the configuration of the band generating device, thereby reducing the circuit scale and the power consumption. .

Further, in the present invention using the cell timing signal from the physical layer, since the physical layer side of the ATM terminal does not require a FIFO memory for storing cells,
The scale of the M cell output circuit can be reduced, and the real-time property of data can be improved.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing a cell output method in ATM transmission.

FIG. 2 is a diagram showing a conventional output circuit configuration of an ATM cell in an ATM terminal device.

FIG. 3 is a diagram showing an overall configuration of a traffic shaping device having a conventional configuration.

FIG. 4 is a block diagram of a conventional band generation unit in the traffic shaping device.

FIG. 5 is a block diagram illustrating a configuration of a band generation device according to the first embodiment of the present invention.

6 is a diagram illustrating a configuration example of a traffic shaping device when the band generating device of FIG. 5 is adopted;

FIG. 7 is a diagram showing an output circuit configuration of an ATM cell when the band generating device of FIG. 5 is employed.

FIG. 8 is a block diagram illustrating a configuration of a band generation device according to a second embodiment of the present invention.

[Explanation of symbols]

 500a to 500n Output timing generation unit 502 Output timing counter 504 Decoder 506 Input cell counter 508 Decoder 510 Logical product operation circuit 606 Band generation unit 608 Contention control unit 700 Frame generation control unit 702 Traffic shaping device 704 Frame generation unit 800 Band generation device 802 Counter 804 cell interval decoder

Claims (4)

[Claims] 1. A band generation device of an ATM traffic shaping device for generating a rate at which an input cell is output to a communication network, the output timing of a corresponding cell being counted for each channel. An output timing counter corresponding to the number of channels to be output, and counter activation means corresponding to the output timing counter for generating an activation signal for starting counting by each of the output timing counters. And a counter starting unit that outputs the start signal when a signal indicating that a cell is present is input and an output timing signal of the cell is input. 2. Each of the counter activation means includes: an input cell counter for counting the number of corresponding cells in an ATM traffic shaping device; and indicating presence or absence of the corresponding input cell according to an output of the input cell counter. A decoder that outputs a signal, and a logic circuit that outputs a start signal of the output timing counter when a signal indicating that there is a corresponding input cell is output from the decoder and an output timing signal of the cell is input. The band generation device according to claim 1, comprising: 3. The band generation apparatus according to claim 1, wherein the cell output timing signal provided to each of the counter activation units is a cell output timing signal generated by a transmission line interface unit of a physical layer. 4. The band generating apparatus according to claim 1, further comprising a 6-bit counter for generating an output timing signal of a cell supplied to each of said counter activating means.