JPS60237766A - Error detecting circuit - Google Patents

Abstract

PURPOSE:To detect an error effectively without requiring the correct amount of information from the outside by deriving the value of the correct amount of information for error detection from decoded information. CONSTITUTION:Encoded image information 11 is decoded by a decoding circuit 31 to obtain decoded image information 12 and a counting circuit 35 counts the amount of decoded image information 12. Then, a control circuit 32 allows a register 33 to hold the amount of information on the 1st line of image information with a signal 36 from the control circuit 32 when the amount of information is outputted from the counting circuit 35 in response to an end-of-line EOL signal 15 supplied from the decoding circuit 31. Then, the control circuit 32 receives a one-line end signal, i.e. EOL detection signal 15 from the decoding circuit 31 for every line and checks the output of a comparing circuit 34, i.e. comparison result signal 16 in response to the received signal to output the result as an output signal 14.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an error detection circuit for detecting errors in decoded information.

(Prior art) Binarized image information such as facsimiles requires a much larger amount of information to handle than general numerical data, so it is important to minimize redundancy to reduce the amount of information to be handled. The data must be compressed before being transferred or stored.

A commonly used compression method is to utilize the characteristics of image information to replace the binary code with a code that corresponds to the continuity of the binary code.

An example of the format of image information encoded in this manner is shown in FIG. In Fig. 1, the encoded data for every l line is separated by a special code called EOL (End of Line).
The end of a page can be known by consecutive EOL codes.

After transferring or storing image information compressed in the format shown in FIG. 1, when outputting it again as image information, it is necessary to decompress the compressed information and restore it to its original form. In this case, decoding is performed using a method opposite to the encoding method used for compression, but if for some reason the contents of the code are incorrect when transferred or stored in compressed format, it may not be possible to decode correctly. becomes impossible.

On the other hand, image information has the property that the amount of information per line is constant, so when decoding compressed information, this property can be used to know whether the decoded information is correct or not. I can do it.

FIG. 2 shows a conventional decoded data error detection circuit. Second
In the figure, encoded image information 11 is a-coded by a decoding circuit 1 and output as decoded image information 12. When encoded data in the format shown in FIG. 1 is given as image information 11 in FIG. 2, when the first EOL code is detected by the encoder circuit 1, an EOL detection signal 15 is output.

When the control circuit 2 receives the EOL detection signal 15, it provides the register 3 with a value that is determined as the amount of image information for one line that has not been decoded.

The decoded image information 12 is output to the outside and is also provided to the counting circuit 5, where the amount of image information is counted. The comparison circuit 4 compares the contents of the register 3 and the contents of the counting circuit 5 to determine whether they are equal. When the decoding circuit 1 detects the EOL code again after decoding one line, the control circuit 2 outputs the comparison result signal 16 which is the output of the comparison circuit 4.
tl - Check.

If the comparison result signal 16 indicates that they are not equal, the decoded image information 12 at that time is erroneous, and an erroneous image detection signal 14 is output. Since the value given by the control circuit 2 to the register 3 differs depending on the size of the image information to be handled, etc., the control circuit 2 is given information regarding the size of the image information to be handled by an external control signal 13.

Therefore, in the conventional circuit described above, when there are many types of image information to be handled, such as the size of the image information, the control regarding the reception of the control signal 13 related to the image information becomes complicated for both the external circuit and the error detection circuit. There are drawbacks.

(Object of the Invention) The object of the present invention is to set the amount of information obtained as a result of decoding the decoded information, for example, the encoded image information of the first line, as a temporary error-free value, and to By using the value for comparison with the result, there are various sizes of image information that can be handled = h
An object of the present invention is to provide an error detection circuit that can operate without receiving a control signal from the outside even when the information is decoded. and a comparing means for comparing the contents of the counting means and the contents of the register.

(Example) Examples of the present invention will be described in detail with reference to the drawings.

FIG. 3 is a block diagram showing one embodiment of the present invention. The erroneous BW output circuit in FIG. 3 includes a decoding circuit 1 which inputs the encoded image information 11 in the format shown in FIG. 1 and outputs the decoded image information 12, and a counting circuit which inputs the decoded image information 12. 35, a register 33 that holds the output of the counting circuit 35, a comparison circuit 34 that compares the value of the counting circuit 35 and the value of the register 33, and a control circuit 32 that controls each of these circuits.

The encoded image information 11 is decoded by the decoding circuit 31 to obtain the decoded image information 12, but the counting circuit 35
The amount of the output decoded image information 12 is counted. When the information amount of the first line of image information is output from the counting circuit 35 in response to the supply of the EOL detection signal 15 from the decoding circuit 31, the control circuit 32 converts the output value into a signal 36 from the control circuit 32. The register 331C is held.

Thereafter, the control circuit 32 receives a signal indicating the end of one line, that is, an EOL detection signal 15, from the decoding circuit 31 for each line, and in response, checks the comparison result signal that is the output of the comparison circuit 34, and sends the result to the output signal 14. Output as .

If the value on the first line is incorrect, the comparison results between the first line and the second line will not be equal, but in such a case, the counting result on the second line can be stored in the register 33 using the signal Error detection for the third line and subsequent lines can be performed. In this case, the data on the ml line should be picked up as invalid data, but such processing is also performed in the conventional system.

As described above, in the third embodiment, it is possible to detect errors in image information even without receiving a control signal related to the size of image information from the outside.

. . . Erroneous detection signal, 15 . . River/EOL detection signal, 16 . . . Comparison result signal.

Claims (1)

[Claims] 1f of decoded information, a counting means for counting, a register for holding the output contents of the counting means, and a comparison means for comparing the contents of the counting means and the contents of the register. Detection circuit.