JPS5836865B2 - Data transmission system and its receiving circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a data transmission system and its reception circuit, and by selecting one of a plurality of Hamming code data as a framing code, the cost of the reception circuit can be reduced and reliable data can be obtained. The purpose of this invention is to provide a data transmission method that can perform data transmission.

Conventionally, in order to achieve frame synchronization in serial transmission, there has been a framing code prefix type data transmission system that includes a framing code with a predetermined always constant bit arrangement and Hamming code data in the data group of the information to be transmitted following the framing code. Are known.

FIG. 1 shows a block diagram of an example of a receiving circuit of a conventional data transmission system.

In the figure, reference numeral 1 denotes an input terminal into which the above-mentioned framing code prefix type data schematically shown in FIG. Serial-to-parallel conversion is performed in synchronization with the next clock pulse.

The parallel output of this shift register 2 is divided into two, and one is supplied to a Hamming code data correction circuit 4, where, for example, Hamming code data is converted into information bits X1, X2 +
X3 + X4, check bit F Cl y C2 p
C3 and parity bit C4, and if the relational expression of check bit CI + C2 t C3 is satisfied, even if there is an error of 1 bit or less in Hamming code data, Hamming can be performed accurately using well-known calculations. Code data is corrected.

Here, ■ in equation (1) represents addition modulo 2 (addition mod 2).

The other parallel output of the shift register 2 is supplied to a flaming code detection circuit 5, where the 8-bit flaming code J 11100101 J shown as an example in FIG. 2 is detected, and upon detection, a detection output is output.
From this point, reproduction of the output data of the Hamming code data correction circuit 4 is started (timing of information processing is determined).
.

In Fig. 2, the flaming code is the well-known l-11100 as an example of an 8-bit code pattern.
101 J.

In the receiving circuit of the conventional data transmission method described above, in order to accurately detect the framing code even when there is an error of 1 bit or less in the framing code data, the flaming code detection circuit 5 uses the following equation as is well known. need to be satisfied.

Detection output = A-B-C-F-H・(D-E-G+D-E
-G+D-E-G+D-E-G) +D-E-G(F-
H・(A-B-C +.A-B-C+A-B-C)+A
-B-C(F-H+F-H) ) (
2) However, in formula (2), A-H indicates each bit output of the shift register 2, and A is the most significant bit (MSB) of them.

However, if the flaming code detection circuit 5 is
) If the formula is satisfied using general logic elements, the circuit configuration would be complicated and the receiving circuit would be expensive. Especially in a data transmission system where there are many receivers, such a receiving circuit would be expensive. The disadvantage of having one was even more undesirable.

The present invention eliminates the above-mentioned drawbacks, and one embodiment thereof will be described with reference to the drawings from FIG. 3 onwards.

FIG. 3 schematically shows signal waveforms transmitted in the data transmission system according to the present invention.

In the figure, X1X4 are information bits, c1 to c3 are check bits, c4 is a parity bit, and c1 to c3 are (
If formula 1) is satisfied and c4 is an odd parity, these will be as shown in the following table.

From the table above, data "10" is flaming code l-1
It can be seen that the bit arrangement is exactly opposite to that of 1100101J.

Therefore, in the method of the present invention, the bit arrangement of the Hamming code is reversed as shown in FIG. ) and the flaming code data, and the Hamming code data correction circuit can be used as a part of the flaming code detection circuit.

Even if the bit arrangement of the Hamming code data is changed in this way, the probability that a flaming code will be erroneously detected from an overlapping group of a flaming code and a data group does not change.

This is because Hamming code data that satisfies the above formula (1) is not fixed data in which all bits have a binary value of 1 or O.

Next, an embodiment in which the method of the present invention is applied to teletext broadcasting will be described.

Currently, various methods have been proposed for teletext broadcasting, but here, as shown in Figure 4A, a character or graphic pattern is inserted into the IH (H is the horizontal scanning period) within the vertical blanking period of the television signal. A digital signal (data group) obtained by horizontal scanning and a control signal S such as a clock run-in and a flaming code at a position temporally earlier than the digital signal (data group).

A method in which the and is time-division multiplexed will be explained.

The clock line-in is a single frequency pulse with a predetermined repetition frequency, as shown in FIG. 2B, and is added to generate a clock pulse with a predetermined phase in the receiving circuit.

FIG. 5 shows a circuit diagram of an embodiment of a receiving circuit when the system of the present invention is applied to teletext broadcasting.

In the figure, the same parts as in FIG. 1 are designated by the same reference numerals, and their explanations will be omitted.

The parallel output signal of the shift register 2 is applied to a Hamming code data correction circuit 6, where, like the Hamming code data correction circuit 4, even if there is an error of 1 bit or less, the Hamming code data is corrected and extracted accurately. It will be done.

The output signal of the Hamming code correction circuit 6 is NAN
The pulse from the input terminal 8 is NANDed with the pulse from the RS flip-flop consisting of two NAND gates 10 and 11, and Hamming code data matching the flaming code is detected. be done.

That is, a control signal S as shown in FIG. 4A is input from the input terminal 8.

A pulse that goes high only in 1H within the vertical blanking period of the television signal on which the data consisting of the data group and data group is superimposed is received.

In addition, a horizontal synchronizing signal or a pulse that goes low for each H in synchronization with the horizontal synchronizing signal enters one input terminal 9 of the NAND gate 11, and resets the RS flip-flop made up of NAND gates 10 and 11 for each H. .

The Q output of this RS flip-flop (output of NAND gate 11) is applied to one input terminal of the NAND gate 7.

As a result, during the IH period in which transmission data of the framing code prefix type transmission system exists, the framing code that always exists at a position temporally earlier than the data group is enabled from the output signal of the Hamming code data correction circuit 6. It is first detected by the NAND gate 7 in the state.

When this flaming code is detected, the NAND gate
The output of 7 becomes low level, which causes NAND
Output of gate 10 is high level, NAND gate 10
1 becomes low level (RS flip-flop consisting of NAND gates 10 and 11 is set).

Therefore, the output of the NAND gate 7 becomes high level again, so that a narrow pulse-like detection signal of negative polarity is obtained at the output terminal of the NAND gate 7 when the flaming code is detected.

Incidentally, at the same time, the NAND gate 7 is brought into a disabled state.

In addition, the data signal output from the Hamming code data correction circuit 6 after the flaming code is detected may include Hamming code data (here, "11100101") having the same bit arrangement as the flaming code. Since the RS flip-flop consisting of NAND gates 10 and 11 is already in the set state, the output of NAND gates 1-11 remains at low level and does not change, and therefore the output of NAND gate 7, which is in the disabled state, remains at high level and does not change. Therefore, Hamming code data having the same bit arrangement as the framing code in the data signal cannot be erroneously detected as a framing code.

As described above, according to this embodiment, the Hamming code data correction circuit 6 can be shared as a part of the flaming code detection circuit in the receiving circuit, so the receiving circuit can be made at a lower cost than in the conventional data transmission system. It can be configured as follows.

Furthermore, since data appropriately modified by the Hamming code data modification circuit 6 is always used, reliable data transmission can be achieved.

In addition, in the above embodiment, the case where the method of the present invention is applied to teletext broadcasting has been explained. Even if there is no data, the method of the present invention can be similarly applied if the total number of bits of the data group including the framing code and Hamming code data is set to remain constant and do not change.

As described above, the data transmission system and its receiving circuit according to the present invention include error-correctable Hamming code data in the number of information bits in a data group in serial data transmitted in the framing code prefix type data transmission system. Since the above-mentioned flaming code is selected to be the same as any one of the plurality of Hamming code data and transmitted, the Hamming code data, which was conventionally provided separately in the receiving circuit, can be transmitted. Of the correction circuit and the flaming code detection circuit, the Hamming code data correction circuit can be shared as a part of the flaming code detector at the same time, making the configuration of the receiving circuit simpler and cheaper than the conventional method. Therefore, it is particularly suitable for application to a data transmission system in which there are a large number of receiving circuits, and since the data that has passed through the Hamming code data correction circuit is used to detect the framing code, it is reliable ( The present invention is applicable to circuits capable of transmitting and receiving data (since single-bit errors can be corrected), and in particular for receiving said data transmitted within a predetermined period of time during the vertical blanking period of a television signal. It has features such as being suitable.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an example of a receiving circuit using the conventional method, Fig. 2 is a diagram schematically showing an example of the signal arrangement of data transmitted using the conventional method, and Fig. 3 is a diagram showing an example of the signal arrangement of data transmitted using the method of the present invention. Figure 4 schematically showing an example of a signal arrangement of data.
Figures A and B are diagrams schematically showing the transmission data signal waveform and its essential parts when the present invention method is applied to teletext broadcasting, respectively, and Fig. 5 is a circuit system showing an embodiment of the receiving circuit of the present invention method. It is a diagram. 1... Data input terminal, 2... Shift register for serial-to-parallel conversion, 3... Clock pulse input terminal, 4, 6... Hamming code data correction. Circuit 7...NAND gate for flaming code detection.

Claims (1)

[Claims] 1. In a data transmission system in which there is a data group related to information to be transmitted after a framing code for frame synchronization on the receiving side, error-correctable Hamming code data is included in the data group. a plurality of Hamming codes according to the number of information bits, and the framing code is selected to be the same as any one of the plurality of Hamming code data. . 2. A receiving circuit of a data transmission system that receives data in which a data group related to information to be transmitted after a framing code exists in a predetermined period within a vertical blanking period of a television signal while maintaining frame synchronization with the framing code. , the data group includes error-correctable Hamming code data according to the number of information bits, and the framing code is selected to be the same as any one of the plurality of Hamming code data. a series-to-parallel conversion circuit for serial-to-parallel conversion of data, and a Hamming circuit for receiving the parallel output signal of the series-to-parallel conversion circuit as an input signal, correcting at least any error in the Hamming code data, and outputting the corrected data. The code data correction circuit is identical to the flaming code first detected from the output signal of the Hamming code data correction circuit after detecting the horizontal synchronization signal of the television signal or a signal synchronized thereto during the period in which the data exists. 1. A receiving circuit for a data transmission system, comprising a gate circuit group that outputs Hamming code data of a code data as a flaming code detection signal.