JP3039135B2 - Data relay device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data relay apparatus for handling digital data surrounded by delimiters for identifying valid data.

[0002]

2. Description of the Related Art A LAN is a communication network usually occupied by a single organization, and bit-serial data communication is performed between devices interconnected via this network. LAN configuration methods include a ring network and a bus network. In a ring network, a plurality of terminals 52 are connected in a ring by a transmission medium 51 as shown in FIG. A signal transmitted from a certain terminal is reproduced and relayed by an adjacent terminal, sequentially transferred, and finally returns to the original terminal. Usually, all terminals share the transmission medium 51 by distributed control in an equal relationship,
Data can be transferred between any terminals.

As shown in FIG. 7B, serial data transferred in such a ring network is composed of a token indicating an access right to a transmission medium and a frame indicating information to be transferred. The token and the frame are surrounded by a delimiter 53 composed of two or more bits for identifying valid data, as indicated by hatching in the figure, and this is transmitted across a preamble (invalid period) 54 of a predetermined bit. Is done. In the token access operation, the terminal that captured the token and transmitted the frame,
There are a method of transmitting the token to the transmission medium at the same time as collecting the frame returned from the transmission medium and a method of releasing the token immediately after the transmission of the frame.

Usually, in such a ring network,
A specific station has a transmission clock generator stabilized by a crystal oscillator, and other relay stations use the reception clock as it is as a transmission clock. That is, when focusing on the clock system, there is a master-slave relationship (for example,
JP-A-58-150346, JP-A-60-226
249).

[0005]

However, when transmission is performed using the reception clock, the number of relay stations is limited by the accuracy of the reception and transmission systems of the relay stations, or high precision is required depending on the number of required relay stations. Reception and transmission systems are required. Further, if the conversion from reception clock synchronization to transmission clock synchronization is performed while receiving data is serial data, the circuit configuration becomes complicated (see US Pat. No. 4,674,086, FIG. 10). The present invention has been made in view of such circumstances,
It is an object of the present invention to provide a data relay device that enables multi-stage relay even if the accuracy of a transmission system is somewhat poor, and that can improve line use efficiency.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a data relay apparatus for receiving, relaying, and transferring serial data surrounded by a delimiter for identifying valid data via a transmission medium. Delimiter code detecting means for extracting the delimiter code from the synchronized received serial data to generate a delimiter timing signal, and generating a first conversion timing signal synchronized with the reception clock from the delimiter timing signal obtained by this means. Means,
Transmission clock generation means for generating a transmission clock having the expected accuracy in normal operation; and means for generating a second conversion timing signal synchronized with the transmission clock from a delimiter timing signal obtained from the delimiter code detection means,
A serial / parallel converter for converting the received serial data into parallel data with the first conversion timing signal, and a parallel / serial converter for converting the obtained parallel data into serial data again with the second conversion timing signal A means for detecting the time required for the transmitted data to go around the transmission medium and return, and calculating the number of relay stations connected to the transmission medium from this time; anda bit based on the calculated number of relay stations. Means for determining the maximum number of missing bits and setting a preamble for the maximum number of bits.

[0007]

According to the present invention, the transmission by the reception clock is stopped, and a transmission clock generating means unique to the relay station is provided. Then, a delimiter timing signal is generated from the received serial data, and a first conversion timing signal synchronized with the reception clock and a second conversion timing signal synchronized with the transmission clock are generated from the first conversion timing signal. A method is adopted in which received serial data is once converted into parallel data, converted into serial data again with a second conversion timing signal, and transmitted. In this system, the accuracy of the receiving and transmitting systems is not limited by the number of relay stations, and it is sufficient that the accuracy up to the upstream or downstream relay station is guaranteed. Therefore, it is possible to configure a data transmission system that can perform multi-stage relay even if the accuracy of the reception and transmission systems is somewhat poor. On the other hand, in the present invention, while obtaining the number of relay stations,
Since the preamble (invalid data) for data protection is optimized, more efficient data relay becomes possible than in the case where a large preamble is fixedly provided with a sufficient margin.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a main configuration of a data relay device according to an embodiment of the present invention. This data relay device includes a delimiter code detector 1 for detecting a delimiter code of received serial data and generating a delimiter timing signal, and performs a first conversion from a delimiter timing signal obtained from the delimiter code detector 1 and a received clock CK1. A conversion timing signal generator 2 for generating a timing signal, a transmission clock generator 3 for generating a transmission clock CK2 stabilized with, for example, a crystal oscillator having expected accuracy in a normal state, and a transmission clock CK2 and a separation timing signal. It comprises a conversion timing generator 4 for generating a second conversion timing signal, and a buffer 5 for initializing and transmitting received serial data in frame units.

The buffer 5 includes a serial / parallel converter 6 for temporarily converting received serial data into parallel data in units of 8 bits, and a parallel / serial converter for converting the obtained parallel data again into serial data synchronized with a transmission clock. It is constituted by a vessel 7. Controlling the serial / parallel converter 6 is a first conversion timing signal obtained from the first conversion timing signal generator 2. Specifically, the first conversion timing signal generator 2 includes:
This is a frequency dividing circuit that divides the reception clock CK1 by 1/8. Controlling the parallel / serial converter 7 is a second conversion timing signal obtained from the second conversion timing signal generator 4. Specifically, the second conversion timing signal generator 4 This is a frequency dividing circuit that divides the transmission clock CK2 obtained from the transmission clock generator 3 by 1/8.

FIG. 2 is a diagram for explaining the operation of the circuit of FIG.
The first conversion timing signal and the second conversion timing signal ideally have the same fixed period, but have a phase difference δ as shown. Although not shown in FIG. 1, the phase difference δ is obtained by providing a predetermined delay circuit in the second conversion timing signal generator 4, for example. The magnitude of the phase difference δ is preferably set to about half the period of the first and second conversion timing signals. In this case, the phase difference δ is initialized each time a delimiter code is input, so that the shift between the first and second conversion timing signals such that the accumulation between frames becomes a half cycle can be tolerated.

As shown in FIG. 2, the reception clock CK1 is
The received serial data is converted from serial data to parallel data every 8 bits by the first conversion timing signal divided by 1/8, and the transmission clock CK2 is further changed by 1/8.
The parallel data is converted into transmission serial data by the divided second conversion timing signal.

In this embodiment, since a transmission clock unique to the relay station is used, a difference in clock cycle is not accumulated by multi-stage relay as in the conventional system in which the reception clock is used as the transmission clock as it is. In this embodiment, since the initialization is performed in units of frames, if the frame length is limited, the accuracy of the receiving and transmitting systems is required. For example, assuming a data length of 146 bytes and a transmission code differential Manchester format, the maximum allowable range of the phase difference δ between the first conversion timing signal and the second conversion timing signal is 8 bits in the transmission code. (Byte) × 8 (bits) × 2 = 0.34 [%]. Accuracy of general crystal oscillator is 100 [ppm]
Then, in this embodiment, the maximum error between the reception clock and the transmission clock is 200 [ppm] = 0.02 [%], and there is a sufficient margin.

In the present invention, since initialization is performed each time a delimiter code is detected, data bits may be dropped when the number of relay stations is large.
In order to prevent such dropped bits, it is necessary to increase the preamble. However, when a large preamble is fixed, the line use efficiency becomes low when the number of relay stations is reduced. In order to solve this problem, the present invention includes means for optimally setting the size of the preamble according to the number of relay stations. The components will be described below.

FIG. 3 shows a configuration of a portion for optimally setting the size of the preamble of the relay device in this embodiment.
In the token ring, as described above, the access right is obtained by collecting the token, a frame is transmitted instead of the token, and when the frame returns around the transmission medium, the token is collected and the token is collected. To release. The transmission selection circuit 35 is a circuit that replaces such a token with a frame. 3. Frame recovery circuit 31 of FIG.
Corresponds to the circuit of FIG. The counter 33 measures the time from when the frame sending circuit 32 sends out the frame until the frame goes around the transmission medium and is collected by the frame collecting circuit 31. From the measurement result, the arithmetic circuit 34
Calculates the number of relay stations connected to the transmission medium, and instructs the frame transmission circuit 32 to transmit a preamble of the maximum number of bit loss or more corresponding to the number of relay stations.

The operation of setting a preamble according to this embodiment will be described with reference to FIG. D in the figure is a delimiter. FIG. 4A shows a case where the preamble is fixed to 20 bits with a margin. In this case, even if the number of relay stations is reduced and the actual bit omission is one bit, the preamble of 20 bits is continuously transmitted. On the other hand, in this embodiment, as shown in FIG. 4 (b), a period for calculating the number of relay stations is provided to determine the actual number of relay stations, and if the maximum bit loss at that time is 10 bits, Send a 10-bit preamble. Therefore, according to this embodiment, the preamble transmission section is reduced by half from 20 bits to 10 bits, and the line use efficiency is improved accordingly.

There may be a case where the frequency error between the transmission clock and the reception clock is large and the frame length is large, and initialization cannot be performed by serial / parallel conversion or parallel / serial conversion in units of 8 bits as in the above embodiment. FIG. 5 shows this state. The period T1 of the first conversion timing signal and the period T of the second conversion timing signal
2 is large, this is accumulated in one frame, and when the phase difference δ becomes larger than the period T1 of the first conversion timing signal, the serial / parallel converter 6 overflows in the buffer 5 and correct transmission is performed. No data is available. In such a case, it is desirable that the size of the serial / parallel conversion and the parallel / serial conversion of the buffer can be variably controlled.

FIG. 6 shows a relay station configuration of such an embodiment. 1 are given the same reference numerals as in FIG. The first conversion timing signal generator 2 calculates 1 /
It has an 8 frequency divider 21 and a 1/16 frequency divider 22, and has a selector 23 for switching these outputs. Similarly, the second conversion timing signal generator 4 has a 1/8 frequency divider 41 and a 1/16 frequency divider 42, and also has a selector 43 for switching between these outputs. Buffer 5 has two 8-bit serial /
Parallel converters 6a and 6b and two 8-bit parallel / serial converters 7a and 7b are provided. The selector 8 is used to select whether to use only one of the two 8-bit serial / parallel converters 6a and 6b, that is, 6b, or to connect them to a series and expand to a 16-bit serial / parallel converter. It is provided in. In order to control the selectors 23, 43 and 8 of these units, a comparator 9, a determiner 10 and a timer 11 are provided.

In a normal state, the selector 23 selects the output of the 1/8 frequency divider 21 and the selector 43 selects the output of the 1/8 frequency divider 41.
And the selector 8 directly takes the received serial data into the 8-bit serial / parallel converter 6b. This state is the same as in the previous embodiment. When the 8-bit serial / parallel converter overflows, the comparator 9 detects this by overlapping the first and second timing signals as shown in FIG. 10, the selectors 23, 43 and 8 are switched. That is, the outputs of the 1/16 frequency dividers 22 and 42 are selected in the first and second conversion timing signal generators 2 and 4, respectively, and the serial / parallel converters 6a and 6b are connected in series in the buffer 5. As a result, switching between serial / parallel conversion and parallel / serial conversion in units of 16 bits is performed.

If the phase difference between the period of the first conversion timing signal and the phase of the second conversion timing signal is smaller than half the tolerance, measured by the timer 11, the selectors 8, 23, 43 Reduce the size of serial / parallel conversion and parallel / serial conversion. Considering the data transfer time, the smaller the size of the serial / parallel conversion and the parallel / serial conversion, the better. Therefore, in this embodiment, for example, the frame length is long while the high-speed performance is maintained in the normal state, When the deviation from the clock becomes a problem, the size conversion is performed so that the data can be securely initialized.

[0020]

As described above, according to the present invention, the use of a station-specific clock as the transmission clock enables the data transfer system to operate in a multi-stage relay even if the accuracy of the receiver or the transmitter is somewhat poor. It is possible to provide a data relay device that can be configured and that can set the preamble size optimally according to the number of relay stations and improve the line use efficiency.

[Brief description of the drawings]

FIG. 1 is a diagram showing a main configuration of a data relay device according to an embodiment of the present invention.

FIG. 2 is a view for explaining the operation of the apparatus of the embodiment.

FIG. 3 is a diagram showing a configuration of a preamble setting unit of the apparatus in the embodiment.

FIG. 4 is a diagram for explaining an operation of setting a preamble.

FIG. 5 is a diagram for explaining a problem in the apparatus of FIG. 1;

FIG. 6 is a diagram illustrating a main configuration of a data relay device according to another embodiment.

FIG. 7 is a diagram showing a configuration of a ring network.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Separation code detector, 2 ... First timing signal generator, 3 ... Transmitter, 4 ... Second timing signal generator, 5
... buffer, 6 ... serial / parallel converter, 7 ... parallel / serial converter, 8, 23, 42 ... selector, 9
... Comparator, 10 ... Determiner, 11 ... Timer, 31 ... Frame recovery circuit, 32 ... Frame sending circuit, 33 ... Counter, 34 ... Operation circuit, 35 ... Sending selection circuit.

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H04L 7/00 H03M 9/00 H04L 12/42 H04L 25/52

Claims (1)

(57) [Claims] 1. A data relay device for receiving and relaying serial data surrounded by a delimiter code for identifying valid data via a transmission medium and transferring the serial data. A delimiter code detecting means for extracting a code to generate a delimiter timing signal; a means for generating a first conversion timing signal synchronized with the reception clock from the delimiter timing signal obtained by this means; Transmission clock generation means for generating a transmission clock with accuracy, means for generating a second conversion timing signal synchronized with the transmission clock from a delimiter timing signal obtained from the delimiter code detection means, Serial / parameter for converting to parallel data with the first conversion timing signal A buffer having a rel converter, and a parallel / serial converter for converting the obtained parallel data into serial data again by the second conversion timing signal; and a time until the transmitted data goes around the transmission medium and returns. Means for calculating the number of relay stations connected to the transmission medium from this time, obtaining the maximum number of bits of bit loss based on the calculated number of relay stations, and setting a preamble for the maximum number of bits. A data relay device comprising: