JPH04361390A - Discriminator for bar code decoder - Google Patents

Abstract

PURPOSE:To simultaneously operate count and comparation so as to attain high speed processing at low cost while comparation is successively executed. CONSTITUTION:The discriminator consists of a bar width measurement counter 41 measuring the width of the bar of a bar code, a comparator 42 comparating a measured count value B with a previously set threshold value C, a memory 45 storing the threshold C, a latch/memory access generating circuit 44 which loads a first threshold from a memory 45 to the comparator 42 so as to make it to compare it with the count value at the same time when the bar width measurement counter 41 starts measuring the width of the bar and which loads a next threshold when the count value goes over a present threshold so as to make the comparator 42 operate next comparation and a quaternary discrimination counter 46 which counts the number of the times when the count value goes over the threshold by comparing with the comparator 42 and which outputs a bar width value discriminated at the time of the count storage of the bar width measurement counter 41 to a character decode circuit.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a barcode decoder discriminator used for discriminating barcode decoding applied to POS (Point of Sales), FA (Factory Automation), and the like.

0002

2. Description of the Related Art In POS, FA, etc., barcode decoders are used to manage products. To discriminate the width of this barcode decoder, there is a configuration that uses a counter that measures the width and a comparator. In this case, the comparison using comparators can be performed by providing the same number of comparators as the reference value and performing comparison in one operation (parallel comparison), or by performing successive comparison using one comparator. This is done using methods such as:

0003

[Problem to be Solved by the Invention] However, in the above-mentioned conventional technology, when the number of comparators is used as many as the reference value, although high-speed processing is possible, the structure becomes complicated and the cost increases. Although the configuration in which successive approximation is performed using one comparator can simplify the configuration, the comparison takes time and high-speed processing cannot be performed. An object of the present invention has been made in view of the above-described actual state of the prior art, and is to provide a discriminator for a barcode decoder that can achieve high-speed processing at low cost while performing successive approximation.

0004

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a discriminator for a barcode decoder for discriminating the width values of a black bar and a white bar after detecting a margin start of a barcode scanner output. , a counter that measures the width of a bar of a barcode, a comparator that compares the measured count value with a preset threshold value, a memory that stores the threshold value, and a counter that measures the width of the bar. At the same time as starting, a first threshold value is loaded from the memory into the comparator and compared with the counted value,
means for loading the next threshold value and performing the next comparison when the threshold value is exceeded, and counting the number of times the counted value exceeds the threshold value by the comparison by the means, and making a discrimination when the counter stops counting. and an n-value discrimination counter that outputs the bar width value. Further, in order to obtain a threshold value that follows variations in bar width, the memory is configured to include means for loading a threshold value corresponding to the length of the bar into the comparator using the count value of the counter as an address. can do.

[0005]

[Operation] According to the above-mentioned means, based on successive approximation, counting and comparison operations are performed at the same time, and the number of times the count value exceeds a threshold value is counted during comparison, and the point at which the counter stops counting operation is counted. The bar width value discriminated by the discrimination counter is output. Therefore, high-speed processing can be achieved with a simple configuration. Further, by storing a threshold value in a memory and reading out the threshold value using a count value as an address, the threshold value that follows the variation of the bar width can be latched into a comparator and compared. Therefore, discrimination can be performed in synchronization with variations in bar width.

[0006]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a discriminator for a barcode decoder according to the present invention, and FIG. 2 is a block diagram showing a schematic configuration of a barcode decoder to which the discriminator of FIG. 1 is applied. First, the configuration of FIG. 2 will be explained. An input buffer 2 for storing the output signal of the barcode scanner 1 is connected to the barcode scanner 1, and a margin start detector 3 for detecting a margin start in the barcode is connected to the input buffer 2. A 4-value discriminator 4 is connected to the margin start detector 3 as an n-value discriminator for discriminating its output signal (here, an example of a 4-value barcode). A character decoding circuit 5 for decoding is connected. An output interface 6 for sending decoding results to a host computer 7 is connected to the character decoding circuit 5.

In the configuration shown in FIG. 2, a binary signal from barcode scanner 1 (black bar is "1", white bar is "0")
) includes signals other than barcode symbols, so
After reading the data stored in the input buffer 2, a margin start detector 3 detects a margin start and identifies the barcode. After the margin start detection is completed, the width values of the black bar and the white bar are identified by the 4-value discriminator 4 and converted into 4-value values. Furthermore, character decoding is performed by the character decoding circuit 5, and the decoded numerical data is sent to the host computer 7 via the output interface 6.

Next, the configuration of the discriminator shown in FIG. 1 will be explained. As shown in FIG. 1, the four-value discriminator 4 includes a bar width measurement counter 41 that starts counting from the rising edge of the black bar using the scanner data A output from the margin start detector 3; Count value B by
an edge detection circuit 43 that generates an edge clock D from the scanner data A, an edge clock D output from this edge detection circuit 43, and a start signal E. and a latch/memory access generation circuit 44 that generates a latch operation and a memory access signal H based on the comparison signal F, a memory 45 that stores the count value B, and a four-value discrimination counter 4 that discriminates the comparison signal F and performs character decoding.
6. Consists of a data latch 47 that latches the count value b and sends it to the memory 45. The latch/memory access generation circuit 44 sends a memory access H and a bit selection signal I to the memory 45, and sends a latch signal G to the comparator 42.

Next, regarding the operation of the configuration shown in FIG.
This will be explained with reference to the timing charts of FIG. 4 (a diagram showing variations in bar width) and FIG. 5 (details of the operation of each part during time X in FIG. 3). When a margin start is detected by the margin start detector 3, the scanner data A output from the margin start detector 3 is sent to the bar width measurement counter 41.
is applied to Here, taking the case of discriminating the width of a black bar as an example, when the black bar rises, the bar width measurement counter 4
1 starts counting and is reset when the black bar falls. The rising edge of the black bar is detected by the edge detection circuit 43. The edge clock D output from the edge detection circuit 43 is applied to the latch/memory access generation circuit 44, and based on this, the latch/memory access generation circuit 44 provides the latch signal G to the comparator 42 to generate the first threshold. Latch the value a. Comparator 4
2 is the count value B of the bar width measurement counter 41 and the memory 45
When the count value B exceeds the threshold value C, the comparator 42 outputs a value at t1=time in FIG.
Since a comparison signal F is output from , the next threshold value b is latched into the comparator 42 using this as a trigger. Thereafter, the threshold values are sequentially latched in the comparator 42 in the same way, and a comparison signal F is outputted from the comparator 42 at each time point t3, t4, . . .
Discrimination processing is performed.

[0010] In this manner, by performing the comparison operation simultaneously with the counting operation, a high-speed discrimination operation is possible. Comparison signal F
is applied to the four-value discrimination counter 46 and counted sequentially to determine how many times the threshold value has been exceeded (5 times in the example of FIG. 4). At the time when the comparator 42 stops counting, the discriminated width value has been output to the four-value discrimination counter 46, and character decoding is then performed.

Next, the threshold values stored in the memory 45 will be explained. The signal from the barcode scanner contains jitter because it outputs an analog signal scanned by a laser as a digital signal. Further, the threshold value must also change following (that is, in synchronization with) changes in bar width due to differences in scanning directions, curvature of barcode labels, and the like. Data latch 47 stores the count value (binary data) of the width of the previous bar at the address of memory 45.
is latched, and the threshold value is selected using this count value as an address. In FIG. 4, the count value B is applied to the lower 8 bits of the address, and the upper 4 bits are applied to the bit selection signal I that selects a to h. A table obtained from actual measurement values is stored in the memory 45, and discrimination is performed in synchronization with variations in bar width.

0012

[Effects of the Invention] Since the present invention is constructed as described above, it achieves the following effects. In the discriminator for a barcode decoder according to claim 1, in the discriminator for a barcode decoder for discriminating the width values of a black bar and a white bar after detecting a margin start of a barcode scanner output, a counter that measures the bar width; a comparator that compares the measured count value with a preset threshold value; a memory that stores the threshold value; means to load a first threshold value from the threshold value and compare it with the counted value, and when the threshold value is exceeded, load the next threshold value to perform the next comparison; Since an n-value discrimination counter is provided which counts the number of times that the bar width exceeds a threshold value and outputs a discriminated bar width value when the counter stops counting, high-speed processing can be achieved at low cost with a simple configuration. Can be done. In the discriminator for a bar code decoder according to claim 2, the memory is configured to include means for loading a threshold value corresponding to the length of the bar into the comparator using the count value of the counter as an address. The threshold value can be made to follow changes in bar width, making it possible to perform discrimination in synchronization with changes in bar width.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the detailed configuration of a four-value discriminator in FIG. 1;

FIG. 2 is a block diagram showing a schematic configuration of a barcode decoder to which a discriminator according to the present invention is applied.

FIG. 3 is a timing chart showing the operation of the embodiment of FIG. 1;

FIG. 4 is a characteristic diagram showing variations in bar width.

5 is a timing chart corresponding to FIG. 4 and showing details of the operation of each part in the time width X of FIG. 3;

[Explanation of symbols]

1 Barcode scanner 2 Input buffer 3 Margin start detector 4 4-value discriminator 5 Character decoding circuit 6 Output interface 41 Bar width measurement counter 42 Comparator 43 Edge detection circuit 44 Latch/memory access generation circuit 45 Memory 46 4-value discrimination counter 47 Data latch A Scanner data B Count value C Threshold D Edge clock E Start signal F Comparison signal G Latch signal H Memory access signal I Bit selection signal

Claims (2)

[Claims] Claim 1: A discriminator for a barcode decoder for discriminating width values of a black bar and a white bar after detecting a margin start of a barcode scanner output, comprising: a counter for measuring the width of a barcode; a comparator for comparing the counted value with a preset threshold value; a memory in which the threshold value is stored; and a first threshold value is loaded from the memory into the comparator at the same time as the counter starts measuring the width of the bar. means to compare the counted value with the counted value, and when the threshold value is exceeded, load the next threshold value and perform the next comparison; and a means for calculating the number of times the counted value exceeds the threshold value by the comparison by the means. A discriminator for a bar code decoder, comprising: an n-value discrimination counter that counts and outputs a bar width value discriminated when the counter stops counting. 2. The bar code decoder according to claim 1, wherein the memory has means for loading a threshold value corresponding to the length of the bar into the comparator using the count value of the counter as an address. Discriminator.