JPS58213542A - Device for detecting and correcting of error of hamming code - Google Patents

Abstract

PURPOSE:To detect and correct an error at a high speed, by adding a Hamming code before correction is added to an address input of a memory and reading out a corrent Hamming code previously stored as data or a code indicating the detection of an incorrectable error from said memory. CONSTITUTION:Nine addresses in A1 correspond to a correct code and one bit error code in the codes of Hamming code No.al. The correct code (00001110) and the one bit error code (other eight-bit code) are the addresses as they are. All the stored data corresponding to the nine addresses are the correct code of the code No.al. The same rule is applied to A2 and thereafter. All the data stored in the memory which correspond to the addresses included in Z are 11111111 and are not included in the Hamming codes shown in the figure, indicating that detection of an incorrectable error. If a Hamming code before correction is inputted to said memory address input, one bit error correction or error correction of two bits or more is detected instantaneously.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an error correction and detection device for a Hamming code to which a 1-bit correctable check bit is added.

A Hamming code to which a 1-bit correctable check bit is added is used, for example, in television teletext broadcasting.

According to the report of the Radio Technology Council in March 1982, television teletext broadcasting is carried out using the method described below.

On the teletext screen, this section is a small section (color block) based on the full-page fixed display page (full display section).
divided into The number of color blocks that make up the entire display section is
The result is a combination of 527 blocks of 31 blocks horizontally and 17 stages vertically. The number of pixels constituting a color block is 8 dots horizontally x 112 dots, and the entire display section is composed of 248 dots horizontally x 204 dots vertically, a total of 50,592 pixels. A horizontal row of pixels is called a pattern line, and the entire display section is composed of 204 pattern lines.

All digital data signals (character signals) for teletext broadcasting, such as dot information and control signals obtained by scanning characters and graphic patterns horizontally and decomposing the image into 248 dots per pattern line, are divided into data packets as a unit. Scanning line numbers 108th (273H in even fields) to 2nd in the vertical m-line interval of the television video signal
Each data packet is time-divisionally superimposed on two arbitrary scanning lines of 1H (No. 2848).

FIG. 1 is a schematic diagram showing the structure of a data packet. Data packets include page control packets (PCP) that transmit control signals related to the entire page such as program number and page number, and color code packets (CCP) that transmit color signals that specify coloring, blinking, concealment, etc. for each color block. ), a pattern data packet (PDP) that transmits binary digital data obtained by horizontally scanning character and graphic patterns (the above-mentioned one pattern line is a PDP1
(included in the packet), a horizontal scroll data packet (HDP) that transmits a signal for horizontal scrolling, a program index packet (PIP) that transmits the program number of the teletext program being transmitted, and a broadcast data packet in the superimposed section. There are six types of dummy packets (DMP) that are sent when transmission is not possible. A data packet consists of a header section and an information data section following it. The header section contains a clock run-in signal (CR) for synchronization, a framing code signal (FC) for frame synchronization, and information indicating the type of broadcasting service. It consists of a service identification/interrupt signal (SI/IN) indicating the type of data packet, and a data identification signal (DI) indicating the type of data packet.
The information data section is composed of pattern data and control signals. The header section consists of 48 bits, the information data section consists of 248 bits, and the entire data packet consists of 296 bits.

FIG. 2 is a schematic block diagram showing an example of the pupil of a television teletext receiver. In the configuration, the parts constituting an ordinary television receiver include a tuner 2 to which an antenna 1 is connected, and a cathode ray tube 13 via an intermediate frequency amplification circuit 3, a video amplification circuit 16, and an output interface circuit 12.
connected to and configured. In the character signal receiving part, the intermediate frequency amplification circuit 3 is connected to the buffer 7 memory 5 via the sampling circuit 4.
, a buffer memory 5, a central processing unit (CPU) 6 such as a microprocessor, a pattern memory 7, a color memory 8, a program selection device*io, a ROM 14, and a RAM.
15 are connected to each other through a pass line 9, and a continuous control circuit 11 is connected to the pattern memory 7 and color memory 8.
The pattern memory 7 and the color memory 8 are connected to the output interface circuit 12.

In operation, a television signal received by the antenna 11 and superimposed with a character signal is channel-selected by the tuner 2 and converted into a video intermediate frequency, and further amplified and detected by the video intermediate frequency amplification circuit 3 and converted into a video signal. Ru. When receiving normal television broadcasting, this video signal is amplified by a video amplification circuit 16 and driven to a cathode ray tube 13 via an output interface circuit 12. On the other hand, in the case of teletext reception, the character signal superimposed on the video signal is separated from the video signal by the sampling circuit 4, and this character signal is temporarily stored in the -H buffer memory 5.

Since the bit rate of the sent character signal is much faster than the data processing speed of the CPU 6, the buffer memory 5 temporarily stores one packet worth of character signal.
The CPU 6 is used to read out the data as necessary until the next character signal arrives. Among the stored character signals, the signal of the teletext program selected by the program selection device f10 is read out from the buffer memory 5 by the CPU 6 and processed, the character pattern data is stored in the pattern memory 7, and the color data is stored in the color memory. 8 via pass line 9 and stored therein. The procedure for the CPU 6 to process character signals is stored in the ROM 14, and the RA
M15 is used for temporary data storage and storage during the processing. Pattern memory 7 and color memory 8
When one page's worth of data is accumulated, the readout control circuit 11 sequentially reads out the stored data, and a character screen is displayed on the cathode ray tube 13 via the output interface circuit 12.

By the way, all the signals of the header part of all the data packets mentioned above, all the signals of the information data part of PCP, CCP, and PIP, and the signals of the information data part of HDP are shown in FIG. 3 [8, It is composed of a 4'l Hamming code.

This is because these signals play an important role in teletext broadcasting, and detection of errors in them is essential.

In FIG. 3, the information bit consists of 4 bits, and 16 types of codes shown by code numbers @81 to a16 are formed.

Four check bits are added to each code, allowing one bit error correction and two bit error detection.

Bit b5 is bit b1. Bit b3. It is the parity of bit b4, and bit b6 is the parity of bit b1° bit b2 .
Parity of bit b4, bit b7 is pit b1
．． Bit b2. Parity of bit b3, bit b
8 is the parity of bit b1 to bit b7. Moreover, the parity is odd parity.

As mentioned above, teletext broadcasts are transmitted superimposed on the vertical blanking period of regular television broadcasts, so
1 vertical return s1! All signals sent during the erasure period must be processed within that period. Therefore, it is required that error correction and detection of the Hamming code described above be performed as quickly as possible.

Therefore, it is an object of the present invention to provide a Hamming code error correction and detection device with high error correction and detection speed.

To summarize, the present invention adds an uncorrected Hamming code to an address input of a memory, and reads from the memory an error-free Hamming code stored in advance as data or a code indicating that an uncorrectable error has been detected. It is something.

The above-mentioned objects and other objects and effects of the present invention will become apparent from the following detailed description with reference to the drawings.

FIG. 4 is a schematic explanatory diagram showing an example of the correspondence between addresses and stored data in a memory used to implement the present invention.

In the figure, nine addresses belonging to A1 correspond to a code with no error and a code with a 1-bit error of the code number a1 of the Hamming code shown in FIG. In the illustrated case, the code with no error (00001110) and the code with a 1-bit error (the other eight codes) are the addresses themselves. All data stored in the memory corresponding to the nine addresses belonging to A1 are code number a.
1 error-free code (00001110).

The same applies to A2 to A16 below.

Addresses belonging to Z range from 256 (all codes consisting of 8 bits) to 9x16-144 (A1 to △1
There are 112 WJ excluding the number of codes belonging to 6), and these correspond to error codes of 2 bits or more of all the codes of code numbers 81 to a16 of the Hamming code shown in FIG. Mote Z
The data stored in the memory corresponding to the address belonging to is all 11111111. 11111111 is the third
This does not exist in the Hamming code shown in the figure, which can indicate that an uncorrectable error has been detected.

In the address input of the memory configured as above,
By inputting the uncorrected Hamming code, one-bit error correction or two or more bit error detection can be instantaneously performed. In other words, for example, if we add the correct code (00001110) with code number @a1 to the address input of the memory, it will be 0000 without error, which is the same as the address man saw.
The output of the stored data at 1110 is selected. Furthermore, if a code with a 1-bit error (for example, 00001111) is added to the address input, an output of error-free stored data of OOOOILLO is obtained, and the 1-bit error is immediately corrected. In this way, one-bit errors can be quickly corrected for all Hamming codes with code numbers 81 to a16.

Furthermore, in the case of an error of 2 bits or more, the input is made to the address belonging to Z, so that the stored data of 11111111 is always output. If 11111111 is determined in advance as information when an uncorrectable error is detected, it is possible to instantly detect errors of 2 or more bits.

In this case, in most cases, the information will not be used.

In addition, in the above embodiment, only the case where the number of bits of the memory address and the number of bits of the Hamming code are the same number, but the number of bits of the memory may be larger than the number of bits of the Hamming code. In this case, the extra bits are predetermined. 0 or 1 may be associated. In this case as well, the same effects as in the above embodiment can be achieved.

In addition, 1111111 is the error detection information of 2 bits or more.
1 was used, but any code that does not exist in the correct Hamming code may be used, and the same effect as in the above embodiment can be achieved.

Further, although only Hamming codes used for character signals of television teletext broadcasting have been described, the present invention is not limited to this and can be applied to all Hamming codes. In this case as well, the same effects as in the above embodiment can be achieved.

As described above, according to the present invention, it is possible to obtain a Hamming code error correction and detection device with high error correction and detection speed.

[Brief explanation of drawings]

Fig. 11 is a schematic explanatory diagram showing the structure of a data packet of a character signal of TV teletext broadcasting, Fig. 2 is a schematic block diagram showing an example of a TV teletext receiving device, and Fig. 3 is a Hamming code used for the character signal. FIG. 4 is a schematic diagram showing an example of the correspondence between memory addresses and stored data used to implement the present invention. In the figure, 1 is an antenna, 2 is a tuner, 3 is an intermediate frequency amplification circuit, 4 is a character signal extraction circuit, 5 is a buffer memory, 6 is a central processing unit, 7 is a pattern memory, 8 is a color memory, and 9 is a pass line. , 10 is a teletext program selection device, 11 is a continuous control circuit, 12 is an output interface circuit, 13 is a cathode ray tube, 14 is a ROM 115 is an R
A.M. Reference numeral 16 indicates a video amplification circuit. Agent Shin Kuzuno - (1 other person) h,)'Fig.

Claims (3)

[Claims] (1) An error correction and detection device for a Hamming code to which a 1-bit correctable check bit is added, comprising a memory having an address corresponding to the Hamming code, and the memory is configured to detect errors in the Hamming code. The error-free code is stored as data at the address corresponding to the code with no error, the code with the 1-bit error corrected is stored as data at the address corresponding to the 1-bit error code of the Hamming code, and the remaining code is stored as data. is a memory that stores a predetermined code from among the codes that do not exist in the Hamming code as data when an uncorrectable error is detected, and adds the Hamming code to the address input of the memory, A Hamming code error correction and detection device further comprising means for reading the stored data from the memory. (2) The Hamming code error correction and detection device according to claim 1, wherein the Hamming code is a Vermink code used for character signals of television teletext broadcasting. (3) The Hamming code error correction and detection apparatus according to claim 2, wherein the Hamming code is an [8,4] Hamming code having 4 information bits and 4 check bits.