JPH09223213A - Counting method and ic card applying this method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To hardly generate data ghosts at the time of rewriting data and to easily judge the generation position of the data ghost by counting one every time changeover to a bit for indicating ON or OFF is shifted for 1-bit in a fixed direction. SOLUTION: For this IC card 1, an IC module 2 with a built-in memory chip composed of an EEPROM is embedded and a counter for counting composed of plural memory bits is formed inside the chip. Then, the counter for counting is turned to 8-bit constitution for instance and is constituted so as to count one every time th changeover to ON (1) of the bit is shifted for 1bit in the fixed direction. For instance, by successively shifting the changeover to 1 to a high-order bit for a count value 0 (decimal number) when all the bits are OFF (0) and the count value 1 (decimal number) when only a least significant bit is 1, the count value is turned to 2, 3 and 8 (decimal number).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an IC card counting method used for prepaid cards and the like, and an IC card using the counting method.

[0002]

2. Description of the Related Art Conventionally, as a counting method using a rewritable read-only memory (EEPROM), a method using a binary number expression is generally used. FIG. 1 shows a counting method of an 8-bit counter using a binary number. In order from the lower bit to the upper bit, 2 ⁰ , 2 ¹ , 2 ² , 2, 2
0 to 25 by weighting ³ , 2 ⁴ , 2 ⁵ , 2 ⁶ and 2 ⁷
Counting up to 5 is possible.

[0003]

By the way, in the binary counting method shown in FIG. 1, when rewriting is performed,
All bits are erased once and then rewritten. In this method, all bits are always rewritable, so if the processing is stopped for some reason during the data rewriting, not only the rewritten value becomes inaccurate, but also in applications such as prepaid cards. In some cases, the data may be garbled such that the value increases despite the subtraction, and it is difficult to determine that the data has garbled.
The present invention is for solving the above-mentioned problems, and
In an IC card using M, a plurality of memory bits are used as a counter for counting, so that data garbling is unlikely to occur at the time of rewriting data, and even if the data garbling occurs, the occurrence position can be easily determined. An object of the present invention is to provide a possible counting method and an IC card using the counting method.

[0004]

According to the present invention, in a counting method in which a plurality of memory bits are used as a counting counter, garbled data is generated by controlling switching between "ON" and "OFF" of adjacent bits. Is less likely to occur, and when garbled data occurs, it is possible to easily identify the position where the garbled data occurs.

[0005]

Embodiments of the present invention will be described below. FIG. 2 is a diagram for explaining a counting method of a counting counter used in the IC card of the present invention, FIGS. 3 and 4 are diagrams for explaining details of data rewriting, and FIG. 5 is a diagram of the IC card of the present invention. It is an external view. The IC card of the present invention is used as a prepaid card or the like. As shown in FIG. 5, the IC card 1 is embedded with an IC module 2 having a built-in memory chip made of an EEPROM.
A counting counter including a plurality of memory bits is formed in the chip. This counting counter has an arbitrary number of memory bits. FIG. 2 shows an example of an 8-bit configuration as the counting counter. The counter of the present invention is configured to count 1 each time one bit is switched in the fixed direction by switching the bit to "ON"("1" in FIG. 2), and all bits are "OFF".
(The count value is "0" (decimal number) when it is "0" in FIG. 2, the count value is "1" (decimal number) when only the least significant bit is "1", and switching to "1" is performed sequentially to the higher bits. By shifting, the count value becomes "2" → "3" → ... "8" (1
It becomes 0 decimal number). Further, when the most significant bit is "1", the switching to "1" is sequentially shifted from the least significant bit to the upper bit to count (add) as "9" → "10" → ... When all the bits are switched to "1", it becomes "36" (decimal number). In the above description, if the "ON" bit and the "OFF" bit are interchanged, it will operate as a subtractor. By thus shifting the ON / OFF of bits in a certain direction and counting, the number of rewriting bits of the data at the time of counting is limited to 2 bits, and since the number of rewriting bits is small, garbled data is less likely to occur. The maximum value that can be represented by this counting method is N · (N + 1) / 2 when N bits are used.

Next, details of data rewriting at the time of counting will be described with reference to FIG. 3 as an example of rewriting from decimal 10 to 11. In the state indicating 10, the second bit is “ON” and the third bit is OFF, as shown in FIG.
Therefore, first, an intermediate 11 'state is created in which the third bit is also turned "ON" (FIG. 3B), and the second bit is continuously turned "OFF" to be 11 (FIG. 3C). . In this way, when shifting “ON” from n bits to n + 1 bits, first, with n bits “ON”, the adjacent n + 1
Create an intermediate state with the bit "ON", then n
Set the bit to "OFF". When rewriting is performed by such a method, in the example of FIG. 3, even if the writing process is interrupted due to some cause in the state of 11 'which is being rewritten, by looking at 11', rewriting from 10 to 11 is in progress. Can be easily determined, and therefore
It is possible to return to the correct value. Although the above description is for addition, an intermediate state may be similarly created for subtraction.

With such a method, the position where the data is garbled can be determined in most cases. For example, 0 →
When the least significant bit is rewritten like the rewriting of 1, 8 → 9, 15 → 16, the above intermediate state cannot be created. Therefore, in the case of dealing with this case as well, as shown in FIG. 4, an auxiliary bit may be provided at the lower order of the least significant bit (or the higher order of the most significant bit). The example of FIG. 4 is for rewriting from 15 to 16, but if the auxiliary bit and the least significant bit are turned “ON” to create an intermediate state, and then the auxiliary bit is turned “OFF”, the same result can be obtained. The effect is obtained.

[0008]

As described above, according to the present invention, the conventional 2
Since the number of rewriting bits is smaller than that in the decimal notation, it is difficult for data to be garbled, and even if data is garbled, it is possible to easily identify the location where the data is garbled. In addition, a great effect can be obtained in preventing illegal use. Further, in the binary representation, the memory bit number is usually changed in units of 4 bits or 8 bits, and the number of memory bits cannot be set arbitrarily, but in the present invention, the number of bits is changed in units of 1 bit. Since it can be changed, it can also be used as a counter of an arbitrary number of bits.

[Brief description of drawings]

FIG. 1 is a diagram showing a counting method of an 8-bit counter using a binary number.

FIG. 2 is a diagram for explaining a counting method of the present invention.

FIG. 3 is a diagram for explaining details of data rewriting.

FIG. 4 is a diagram for explaining details of data rewriting.

FIG. 5 is an external view of an IC card of the present invention.

[Explanation of symbols]

 1 ... IC card, 2 ... IC module.

Claims (4)

[Claims] 1. In a counting method using a plurality of memory bits as a counting counter, "ON" (or "O")
The counting method is characterized in that one is counted every time one bit is shifted in a fixed direction by switching to a bit representing "FF"). 2. The counting method according to claim 1, wherein the counting is in one direction of “increase” or “decrease”. 3. The method according to claim 1, wherein when counting one, a bit representing “OFF” (or “ON”) adjacent to a bit representing “ON” (or “OFF”) is “ON” ( Or "OFF"), and then the bit representing "ON" (or "OFF") is set to "OF".
The counting method is characterized by switching to "F" (or "ON"). 4. An IC card to which the counting method according to claim 1 is applied.