JPH0669932A - Preamble decoding reproduction system for repeater for lan - Google Patents

Abstract

PURPOSE:To implement communication with an efficient preamble length eliminating the need for setting of a preamble length longer in advance while expecting a preamble number lost in the repeater and not especially needing setting revision against extension or reduction of network configuration. CONSTITUTION:The system is provided with a buffer memory 8a buffering tentatively reception data from a medium 1a. A preamble is written in advance to the buffer memory 8a from a pattern generating section 6a via a selector 7a. On the other hand, when a border of a preamble pattern is detected from a frame 5a, a frame detection section 5a generates a selection signal to control continuously writing the reception data after the detected border just after the preamble pattern written in advance in the buffer memory 8a to control the selector 7a. Thus, the decoded frame with the preamble added automatically thereto is outputted to a medium 1b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a preamble restoration / playback system for a repeater device of a bus type local area network, and more particularly to a preamble restoration / playback system for a repeater device having a retiming function.

[0002]

2. Description of the Related Art Conventionally, this type of bus-type local area network (hereinafter referred to as LAN) is expected to cause a bit loss in the repeater device when the repeater device has a retiming function. It is general to add a preamble length that is long enough even if the beginning of the preamble is lost by the amount. For example, I
In the CSMA / CD system as defined in EEE802.3, a so-called Ethernet LAN system, the network configuration rules such as the number of stages of repeater devices and the transmission line length of the trunk line are related to the network configuration in relation to the definition of the collision detection range. Is clearly defined, and the above-mentioned settings can be determined relatively easily within the restriction.

Even if the same bus type LAN is used, IEEE8
In the case of the token passing bus method specified in 02.4, the network scale is determined by the trade-off with the time required to circulate the token, and the network circulates even if the transmission path length and the number of repeater stages increase. Only the cycle of the token is increased and the transmission delay time is increased, and the logical operation of the system is not inconsistent.
In other words, in operation, the target time for token circulation and the slot time for token control should be adapted,
When the repeater device is used in this system, limiting the number of stages of the repeater device or the like is not a good idea for the above-mentioned reason. Therefore,
Calculate the preamble length lost in each repeater device on all routes, and adjust the preamble length attached on the transmission side so that the minimum required preamble length can be secured in the receivers of all terminals considering the maximum value. There is.

[0004]

In order to set the preamble length in the above token passing bus system, it is necessary to grasp the number of preambles lost by each repeater device used. This is a cumbersome task for system construction because it is highly likely that each vendor will differ when operating with multiple vendors, and it is necessary to search for the largest one in all routes in the network configuration. Can be said.

Also, it is necessary to consider that the network has a relatively high possibility of system expansion due to its nature, and if the number of repeater stages of the network route increases at the time of expansion, it is necessary to reset the preamble length for all terminals. As a result, the operational impact will be large. If a sufficiently long preamble length is set in advance in anticipation of the expansion, the complexity of the system configuration is released. However, considering that the data portion of the token is less than 20 bytes, the overhead due to an increase in the number of preambles in each packet is a factor that deteriorates the performance. That is, in the system in which the tokens are constantly patroled at high speed, the performance is significantly deteriorated.

An object of the present invention is to provide a preamble restoration / playback system for a repeater device for LAN which can realize an efficient preamble length even when the network is expanded or reduced without considering the number of preambles lost in the repeater device. To provide.

[0007]

A preamble restoration / playback system for a LAN repeater device of the present invention is a preamble restoration / playback system for a repeater device having a retiming function used in a bus type local area network. Buffer memory for dynamically buffering, a means for writing a preamble pattern defined by a network to be adapted in advance in the buffer memory as data, and a bit pattern of the preamble pattern from an actually received data frame. And a unit for writing a data frame after the detected boundary immediately after the preamble pattern previously written in the buffer memory.

The preamble restoration / playback system of the LAN repeater device of the present invention is a preamble restoration / playback system of a repeater device having a retiming function used for a bus type local area network, in which a preamble pattern is received from a received data frame. Means for detecting the boundary of the bit pattern, a buffer memory of FIFO type for temporarily buffering the data frame after the detected boundary, and a preamble pattern generating means for generating the preamble pattern specified in the network to be adapted. And is configured to transmit the signal generated by the preamble pattern generating means at the time of relaying and then continuously transmit the received data in the buffer memory.

[0009]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a block diagram of a LAN repeater device showing an embodiment of the present invention. As shown in FIG. 1, in this embodiment, the receiver 2a is connected to the medium 1a of the segment on one side. The signal generated on the medium 1a is detected and amplified by the receiver 2a, and the clock component is extracted by the clock extraction unit 3a. The clock extraction unit 3a generates a reception clock synchronized with the reception signal, and the decoder 4
is supplied to a. Next, the decoder 4a outputs the received signal to NR
The Z signal is decoded and converted and supplied to the frame detection unit 5a and the selector 7a. On the other hand, in order to monitor this, the frame detector 5a detects the received data input and selects the selector 7
A selection signal for controlling a is generated. Also, the selector 7a
The pattern output from the pattern generation unit 6a and the transmission clock generated by the transmission clock generation unit 11 are input to the other input. Depending on the selection signal from the frame detection unit 5a described above, the selector 7a receives the received signal or the pattern generation unit 6a.
Or the OFF signal is selectively output and temporarily stored in the buffer memory 8a having the FIFO function. Thereafter, the output of the buffer memory 8a is encoded by the encoder 9a in synchronization with the transmission clock from the transmission clock generator 11, converted into a physical signal by the driver 10a, and then output onto the medium 1b of the opposite segment. It

Next, the relay from the segment medium 1b to the medium 1a is similarly performed. That is, each circuit from the receiver 2b to the driver 10b operates similarly to the circuit from the receiver 2a to the driver 10a described above. Therefore, the description is omitted.

In the present embodiment, the repeater device used in the IEEE802.4 frame format will be described, but the same principle can be applied to other frame formats. The frame format of the received signal will be described below.

2 (a) to 2 (c) are frame diagrams for explaining the preamble addition state in FIG. 1, respectively. First, as shown in FIG. 2A, this format represents a frame of a received signal, and the portion L1 is the preamble portion. Normally, in this method, when the output of the pattern generating section 6a is written in the constant bit number buffer memory 8a in the initial state, the state shifts to the idle state. The pattern generating unit 6a generates a "101010 ..." Pattern, that is, a preamble pattern. When the physical signal from the medium 1a is detected by the receiver 2a in the idle state, the relay state is entered. In this relay state, the clock extraction unit 3a generates a reception clock synchronized with the reception signal based on the level-converted reception signal and supplies the reception clock to each unit. Since the received signal at this time uses a code including a clock component, such as Manchester code or CMI code, the decoder 4a performs decoding conversion and outputs it as an NRZ signal to the selector 7a. At the same time, the received signal is also supplied to the frame detection section 5a, where it matches the bit pattern of the preamble at the head of the frame to search for the boundary point of the preamble data. The preamble is a list of "10101010 ...", but even if the first few bits are missing, it is recognized as a frame when the repeated pattern of "10" is recognized. At this time, the bit pattern “10” is considered as a pair, and this is determined as the boundary. The selection signal from the frame detector 5a is generated in synchronization with the bit pattern "1".
That is, the patterns before that are discarded by switching the input of the selector 7a. As a result, the preamble pattern to be written in advance in the initial state is "1010 ...
If set to 1010 ", the correct preamble pattern can be restored and reproduced when connected on the buffer memory 8a.

Next, as shown in FIG. 2 (b), the received frame of FIG. 2 (a) described above loses part (L3) of the preamble due to clock extraction and frame detection, and becomes the preamble length L2.

Further, as shown in FIG. 2C, although the preamble length becomes short due to loss, an additional preamble pattern of length L4 is previously stored in the buffer memory 8a. Therefore, the frame read and transmitted by the encoder 9a has a frame format of the preamble length L5. The additional preamble length L4 written in advance in the buffer memory 8a is equal to or greater than the maximum number of preamble bits lost by the repeater device. The selection signal is held until there is no received data. Therefore, when there is no received data, the output of the selector 7a turns off and the input to the buffer memory 8a disappears.

However, when the encoder 9a finishes reading the buffer memory 8a and empties the data, the repeater unit shifts from the relay state to the initial state after the transmission of the read data from the driver 10a ends.
The loading of the additional preamble pattern on the buffer memory 8a is executed. If a received signal comes in during this period, the repeater device is not in the idle state and is ignored. It should be noted that the condition is that the input signal is OFF when shifting from the initial state to the idle state.

Further, the circuit of the system from the medium 1a to 1b and the circuit of the system from the medium 1b to 1a of the repeater device in this embodiment can operate independently, and can be operated in the initial state or the idle state. It is premised that the transfer is also performed independently, but if full-duplex operation is not required, this method can be easily realized even if the circuit is shared.

FIG. 3 is a block diagram of a LAN repeater device showing another embodiment of the present invention. As shown in FIG.
In this embodiment, the receiver 2a is attached to the medium 1a of one segment.
Are connected. The signal generated on the medium 1a is detected and amplified by the receiver 2a, and the clock component is extracted by the clock extraction unit 3a. The clock extraction unit 3a generates a reception clock synchronized with the reception signal and supplies the reception clock to the decoder 4a. Next, the decoder 4a outputs the received signal to N
It is decoded and converted into an ARZ signal and supplied to the preamble detection unit 12a. In order to monitor this, the preamble detection unit 12a detects the received data input and detects the pattern generation unit 6a.
a is started, and a selection signal for controlling the selector 7a is generated. As a result, the output of the pattern generator 6a is supplied to the encoder 9a. On the other hand, the received data that has passed through the preamble detection unit 12a is temporarily stored in the buffer memory 8a having the FIFO function, and the pattern generation unit 6a waits until the pattern generation of the additional preamble length is completed.
Then, when a prescribed amount of pattern is sent to the encoder 9a via the selector 7a, the data stored in the buffer memory 8a from the other input of the selector 7a,
That is, the received data is input and selected and output. The reception data output from the selector 7a is synchronized with the transmission clock from the transmission clock generator 11, encoded by the encoder 9a, converted into a physical signal by the driver 10a, and then output onto the medium 1b of the opposite segment. It Also, in the present embodiment, the relay from the segment medium 1b to the medium 1a is performed in the same manner as in the above-described one embodiment.

The present embodiment is also described by assuming a repeater device used in the same frame format as that of the above-mentioned one embodiment, but the same principle can be applied to other frame formats. . The frame format of the received signal will be described below. Also in this case,
Reference is made to FIGS.

Normally, in this system, the receiver 2a does not perform any operation until a signal is detected, and when the receiver 2a detects a received signal, the receiver 2a shifts to a relay state. In this relay state, the clock extraction unit 3a generates a reception clock synchronized with the reception signal based on the level-converted reception signal and supplies the reception clock to each unit. Since the received signal at this time uses a code including a clock component, such as Manchester code or CMI code, it is decoded and converted by the decoder 4a and input to the preamble detection unit 12a as an NRZ signal. The preamble detection unit 12a performs pattern matching with the preamble bit pattern attached to the head of the frame to search for a boundary point of the preamble data. The preamble is a list of "10101010 ...", but even if the first few bits are missing, it is recognized as a frame when the repeated pattern of "10" is recognized. At this time, the bit pattern “10” is considered as a pair, and the boundary is determined here. The first bit pattern of the data recognized as this frame is accumulated in the buffer memory 8a at the subsequent stage from the beginning of "10". As a result, the additional preamble generated by the pattern generation unit 6a is set to "1010".
If set to 10 ... 10 ", the correct preamble pattern is restored and reproduced in the encoder 9a when switched by the selector 7a.

The received frame shown in FIG. 2 (a) is part of the preamble (L
3) is lost and the preamble length is changed from L1 to L2 as shown in FIG. 2B, but the received data is temporarily held and the pattern generation unit 6a changes the length L4 as shown in FIG. 2C. Since the preamble pattern is inserted, the frame transmitted by the encoder 9a has a preamble length L shown in FIG.
The frame format is 5. This pattern generator 6
The additional preamble length L4 inserted from a is equal to or greater than the maximum number of preamble bits lost by this repeater device. Further, the size of the buffer memory 8a (the number of accumulated bits) is determined by the additional preamble length L4 and the necessary amount for absorbing the reception / transmission clock deviation.

Further, the medium 1a in this repeater device
Although it is possible to operate the circuit of the system from 1 to 1b and the circuit of the system from 1b to 1a independently, when full duplex operation is not required, even if the circuit is shared, this method is used. It can be easily realized.

[0022]

As described above, according to the preamble restoration / playback method of the LAN repeater device of the present invention, the preamble lost by passing through the repeater device is automatically restored / played, so that the repeater device can be passed through many stages. However, the preamble length does not decrease, and there is an effect that it is not necessary to consider the preamble length lost in the route even when designing the network. In addition, the present invention has an effect that the optimum preamble length can be easily determined at the time of introduction, the optimum preamble length can be maintained without any change at the time of expansion, and the system performance can be efficiently used.

[Brief description of drawings]

FIG. 1 is a block diagram of a LAN repeater device according to an embodiment of the present invention.

FIG. 2 is a frame diagram for explaining a preamble addition state in FIG.

FIG. 3 is a block diagram of a LAN repeater device according to another embodiment of the present invention.

[Explanation of symbols]

 1a, 1b medium 2a, 2b receiver 3a, 3b clock extraction unit 4a, 4b decoder 5a, 5b frame detection unit 6a, 6b pattern generation unit 7a, 7b selector 8a, 8b buffer memory 9a, 9b encoder 10a, 10b driver 11 transmission clock Generation unit 12a, 12b Preamble detection unit

Claims (2)

[Claims] 1. In a preamble restoration reproduction system of a repeater device having a retiming function used for a bus type local area network, a FIFO type buffer memory for temporarily buffering received data and a network to be adapted in advance are defined. Means for writing the selected preamble pattern as data in the buffer memory, means for detecting the boundary of the bit pattern of the preamble pattern from the actually received data frame, and the data frame after the detected boundary. A preamble restoration / playback system for a LAN repeater device, comprising means for writing immediately after the preamble pattern previously written in a buffer memory. 2. In a preamble restoration / reproduction method of a repeater device having a retiming function used for a bus type local area network, means for detecting a boundary of a bit pattern of a preamble pattern from a received data frame, and the detected means. A FIFO type buffer memory for temporarily buffering data frames after the boundary,
It has a preamble pattern generating means for generating the preamble pattern defined in the network to be adapted, and transmits the signal generated by the preamble pattern generating means when relaying the received data in the buffer memory to it. A preamble restoration / playback method for a repeater device for LAN, which is characterized by continuous transmission.