JPH114185A - Communication system/device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely and securely sample reception data without dropping the communication speed by providing a reset means for resetting a frequency- dividing operation when reception data changes and starting the frequency- dividing operation after prescribed time passes for a main device. SOLUTION: The reset circuit 17 of a card reader/writer outputs a reset signal to a clock frequency-dividing circuit 11 with the rise/fall of reception data and resets the frequency-dividing operation. The reset circuit 17 holds a reset state only for prescribed time t0 after the frequency-dividing operation is set. The clock frequency-dividing circuit 11 is started after prescribed time t0 passes and the frequency-dividing operation is started. The frequency-dividing operation is reset again at timing when next data changes and it is resumed after a prescribed time t0 passes. Reception data of the card reader/writer is sampled by the rise of the reception clock of the card reader/writer, which is the frequency-divided output of the clock frequency-dividing circuit 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication system and an apparatus for communicating between a main apparatus and, in particular, a communication apparatus including a mobile unit.

[0002]

2. Description of the Related Art In a non-contact communication system including a main device such as a card reader / writer and a communication device such as a card which performs non-contact communication with the main device, the driving power of the communication device is not controlled by an internal battery but by the main device. Some are formed based on carrier waves transmitted from the side. In this system, a carrier is transmitted from a main device to a communication device, and the communication device receives the carrier and charges the signal to form an internal drive voltage. Further, by modulating this carrier wave on either the main device side or the communication device side, mutual transmission and reception are enabled.

FIG. 4 shows an overall configuration diagram of a non-contact communication system using a card reader / writer (R / W) 1 as a main device and a card 2 as a communication device. Each of the card reader / writer 1 and the card 2 includes digital sections 1a and 2a for processing data, and analog sections 1b and 2b for modulating and demodulating signals.
1. Two-way communication is enabled by bringing L2 close to each other.
Generally, a control unit such as a personal computer 3 is connected as a host computer of the card reader / writer 1.
In this system, the card 2 has no battery inside. The card reader / writer 1 transmits a carrier to the card 2, and the analog unit 2b of the card 2 receives the carrier and charges a received signal to a capacitor. The charge voltage of this capacitor is converted to the analog section 2b and the digital section 2b.
It is used as the drive voltage of a. When the card reader / writer 1 transmits data to the card 2, the carrier wave is modulated by the card reader / writer 1, and
The card 2 generates a clock from the carrier wave, divides the clock, and samples received data. Conversely, when data is transmitted from the card 2 to the card reader / writer 1, the clock generated from the carrier in the card 2 is frequency-divided, and the divided clock is used to control transmission data transmission timing and the like. Modulate the carrier. The card reader / writer 1 samples the received data by dividing the frequency of the carrier clock.

FIG. 5 shows a more detailed configuration diagram of the analog units 1b and 2b of the contactless communication system shown in FIG.
The analog section 1b of the card reader / writer 1 includes a carrier clock generation section 10 for generating a carrier clock, a clock frequency dividing circuit 11 for dividing the clock to generate a transmission clock and a reception clock, and transmitting transmission data using the transmission clock. The control circuit includes a transmission circuit 12 for performing control, a reception circuit 13 for sampling reception data using the reception clock, a resonance circuit 14 that resonates at the frequency of the carrier clock, and a transmission amplifier 15 and a reception amplifier 16. The analog section 2b of the card 2 is a constant voltage circuit 20 for converting a voltage obtained by charging a carrier reception signal into a constant voltage,
A clock generation circuit 21 for generating a clock equal to the carrier frequency; a clock frequency dividing circuit 2 for dividing the clock to generate a transmission clock and a reception clock for sampling
2. A receiving circuit 23 that samples received data using the receiving clock, a transmitting circuit 24 that controls transmission of transmitting data using the transmitting clock, a resonant circuit 25 that resonates with a carrier, a receiving amplifier 26, and a transmitting amplifier 27.
It has. The capacitor included in the resonance circuit 25 has a function of charging a carrier wave (carrier) signal and supplying the charged voltage to the constant voltage circuit 20 as a power supply voltage.

[0005]

However, in the above non-contact communication system, since the clock at the communication device side (card side) is generated from the carrier wave, the communication device side (card side) switches from the main device side to the main device side. When data is transmitted to the (card reader / writer side), the data may not be normally received by the main apparatus (card reader / writer side). This will be described with reference to FIG. 5A shows a voltage waveform across the coil L2 of the card 2 at the time of resonance, FIG. 5B shows transmission data from the card 2 (reception data of the card reader / writer 1), and FIG. 5C shows a clock generation circuit 21 of the card 2. (D) is divided by the clock dividing circuit 22 of the card 2 and transmitted by the transmitting circuit 24.
(E) shows a card reader / writer reception clock divided by the clock divider circuit 11 of the card reader / writer 1 and output to the reception circuit 13. Note that, as shown in FIG.
Performed by the K modulation method, and the card transmission data is "1"
When the modulation degree is several tens%, when it is “0”, the modulation degree is 10
Set to 0%.

The following descriptions (1) to (7) correspond to (1) to (7) in the drawing.

(1) When the card transmission data changes from “0” to “1”, or vice versa, from “1” to “0”
, The Q of the coil L2 of the card 2 becomes unstable, and the voltage between both ends of the coil L2 also becomes unstable.

(2) When the voltage between both ends of the coil L2 becomes unstable, the card clock (reception carrier) output from the clock generation circuit 21 is multiplied.

(3) Clock frequency dividing circuit 22 of card 2
Generates a card transmission clock by dividing the card clock and outputs it to the transmission circuit 24. The transmission circuit 24
The transmission timing is controlled by the card transmission clock.

(4) In the card reader / writer 1,
The clock divider circuit 11 having the same frequency division ratio as the clock divider circuit 22 on the card 2 generates a card reader / writer receive clock and outputs it to the receiver circuit 13. However, as shown in the figure, the card transmission clock on the card 2 side generated in (3) is slower than the card reader / writer reception clock because of the card clocking.

(5) The card 2 sends 1-bit data at the falling timing of the card transmission clock.

By repeating the above operation, T1, T1
Since the card clock is delayed by one card clock in each one bit transmission section of T3 and T5, a total of three card clocks are delayed in the stage of T5. As a result, (6) and (7) a phenomenon occurs in which the 1-bit data is sampled twice by the card reader / writer reception clock on the card reader / writer 1 side. That is, for the 1-bit transmission data from the card 2, the reception data of the card reader / writer 1 is 2 bits.

As described above, when the transmission timing of the card transmission data is controlled by the card transmission clock generated based on the reception carrier, the card clock is multiplied, and the card transmission data and the card transmission data are accumulated. There was a problem that the data received by the reader / writer did not match.

In order to solve the above problem, a crystal oscillation circuit or a PLL circuit is provided in the card 2 so that the operation clock and the card transmission / reception clock are the same in both the card reader / writer and the card reader / writer. A method of providing a PLL circuit on the side and correcting the card reader / writer reception clock may be considered. However, if a crystal oscillation circuit or a PLL circuit is provided on the card side, there is a problem that the circuit becomes complicated and power consumption increases. In addition, in a method in which the PLL circuit is provided on the card reader / writer side, since the PLL circuit is used, There is a problem that time is required to receive the preamble data from the side in advance and communication becomes difficult for a short time. Also, since the communication speed of the transmission data from the card varies depending on the conditions,
There is also a problem that it does not always operate at the frequency according to the preamble supplied to the L circuit.

An object of the present invention is to provide a communication system and a communication system capable of accurately receiving transmission data from a communication device by utilizing data received by a main device (card reader / writer) also for clock synchronization. It is to provide a main device to be used.

[0016]

According to the first aspect of the present invention, there is provided a main apparatus for dividing a carrier clock to perform transmission data transmission control and sampling received data, and for generating a clock from a carrier of a received signal. In a non-contact communication system comprising: a communication device that generates and divides the frequency, performs transmission control of transmission data and samples reception data, the main device resets a frequency division operation when reception data changes. And a reset means for starting the frequency division operation after a lapse of a predetermined time.

Further, the invention according to claim 2 is characterized in that the main device is a card reader / writer, and the communication device is a non-contact card which communicates with the card reader / writer in a non-contact manner.

Further, the invention according to claim 3 is characterized by the configuration of the main device in the invention according to claim 1.

In this communication system, the main unit resets the reception clock for sampling the reception data when the reception data changes, that is, at the rising edge or the falling edge. Does not affect until the next data changes. For example, in the example shown in FIG.
The delay of the card clock is not introduced in the next data change period T3. Similarly, the clock delay generated at T3 is not brought to T5. in this way,
Since the reception clock for sampling the reception data on the main unit is reset every time the data changes, the clock delay does not gradually accumulate, so that the main unit can transmit 1-bit transmission data by a plurality of bits. The problem of reading as data can be eliminated.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of a main part of a contactless card system according to an embodiment of the present invention.
The difference from the conventional system shown in FIG. 5 is that the card reader / writer 1 is provided with a reset circuit 17 for resetting the clock frequency dividing circuit 11 at the rise and fall of the received data. FIG. 2 is a time chart showing the operation of the contactless card system.
The operation of the contactless card system will be described below with reference to FIG.

FIG. 3A shows the coil L of the card 2 at the time of resonance.
(B) is the transmission data from the card 2 (reception data of the card reader / writer 1), (c) is the card clock output from the clock generation circuit 21 of the card 2, and (d) is the card 2 A card transmission clock divided by the clock dividing circuit 22 and output to the transmitting circuit 24;
(E) is a clock divider circuit 11 of the card reader / writer 1
Represents a card reader / writer reception clock that is divided by and output to the reception circuit 13, and (f) represents a carrier clock generated by the card reader / writer 1. In addition, FIG.
The modulation is performed by the ASK modulation method as shown in
When the card transmission data is "1", the modulation degree is several tens%,
When "0", the modulation factor is set to 100%.

The following descriptions (1) to (7) correspond to (1) to (7) in the figure.

(1) When the card transmission data changes from “0” to “1”, or vice versa, from “1” to “0”
, The Q of the coil L2 of the card 2 becomes unstable, and the voltage between both ends of the coil L2 also becomes unstable.

(2) When the voltage between both ends of the coil L2 becomes unstable, the card clock (reception carrier) output from the clock generation circuit 21 is multiplied.

(3) Clock divider circuit 22 of card 2
Generates a card transmission clock by dividing the card clock and outputs it to the transmission circuit 24. The transmission circuit 24
The transmission timing is controlled by the card transmission clock.

(4) The reset circuit 17 of the card reader / writer 1 issues a reset signal to the clock frequency divider circuit 11 at the rise and fall of the received data to reset the frequency division operation.

(5) The reset circuit 17 holds the reset state for a fixed time t0 after resetting the frequency division operation.

(6) After a lapse of a predetermined time t0, the clock frequency dividing circuit 11 starts and starts a frequency dividing operation. This frequency division operation is performed at the next data change timing (for example, T2
The timing is reset again at the timing of shifting from T3 to T3), and is restarted after the elapse of the predetermined time t0.

(7) The card reader / writer reception data is sampled at the rise of the card reader / writer reception clock which is the frequency division output of the clock frequency divider circuit 11. The fixed time t0 is for slightly delaying the frequency division activation time so that the sampling is not at both end positions of the card reader / writer reception data length but near the center position as much as possible. This constant time t0 is a time including zero, since there is no need to carry out.

In the example shown in FIG. 2, T1, T3, T4, T
5 at the beginning of each period, T1, T3, T5
, A card clock is generated, and a delay is caused accordingly. However, even if a clock delay occurs in each of the periods T1, T3, and T5, since the card reader / writer reception clock is reset at the first timing of each of the periods T1, T3, and T5, those clock delays are reduced. It is not carried over and accumulated after reset.
Therefore, the sampling timing does not arrive a plurality of times during the period of one bit of the card transmission data. As a result, sampling of the card reader / writer reception data (card transmission data) can be performed reliably and accurately. When the PLL circuit is provided on the card reader / writer side, it is necessary to add preamble data to the card transmission data. However, in the system of the present embodiment, it is not necessary to provide such preamble data, so that the communication time is long. It will not be. Also, card 1
Can be exactly the same as the conventional configuration shown in FIG. 5, so that low power consumption and circuit simplicity are maintained.

FIG. 3 is a circuit diagram of the reset circuit 17. The counter CT is reset by receiving a reset pulse at the rise and fall of the data received by the card reader / writer, then counts the carrier wave clock and outputs “L” until the time t0 elapses.
Since this signal is output to the reset terminal R of the clock frequency dividing circuit 11, the frequency dividing circuit 11 is reset at the rise and fall of the data received by the card reader / writer, and performs the frequency dividing operation only during the period of t0. And t0
After elapse, the frequency division operation is started.

In the above embodiment, the non-contact card system of the ASK modulation system has been described. However, the present invention is applied to the FSK modulation system and the PSK modulation system in which the waveform is disturbed when the data transmitted from the card changes. Accurate and reliable sampling of the writer reception data becomes possible. A communication system according to the present invention is a shopping system in which a card is attached to a product as a tag, a plurality of products selected by a customer for purchase are placed in a production corner and automatically processed, and each conveyed product conveyed on a belt compare. Applied to a transport system that attaches tags and recognizes them at a specific location collectively, a warehouse management system that attaches tags to each item stored in the warehouse, and identifies them at a specific timing such as when the power is turned on can do.

The main device and the communication device are not limited to a card reader / writer and a card, and any communication device can be applied. Further, the present invention is applicable not only to a non-contact communication system but also to a contact type communication system.

[0034]

According to the present invention, even if a PLL circuit is not provided on the main device side or a crystal oscillation circuit or a PLL circuit is provided on the communication device side, accurate and reliable reception can be performed without reducing the communication speed. Data sampling can be performed.

[Brief description of the drawings]

FIG. 1 is a main part configuration diagram of a contactless communication system according to an embodiment of the present invention;

FIG. 2 is a time chart for explaining the operation of the system.

FIG. 3 is a circuit diagram of a reset circuit.

FIG. 4 is a configuration diagram of the contactless card system.

FIG. 5 is a configuration diagram of a main part of a conventional contactless card system.

FIG. 6 is a time chart showing the operation of the conventional contactless card system.

Claims (3)

[Claims] 1. A main device for dividing a carrier clock to perform transmission data transmission control and receiving data sampling, a clock being generated from a carrier of a reception signal, dividing the frequency, and controlling transmission data transmission. A communication device for sampling received data, wherein the main device is configured to generate a sampling clock for sampling the received data by dividing the carrier clock by a frequency divider; The main device resets the frequency divider when the received data changes, and includes a reset unit that starts the operation of the frequency divider after a lapse of a predetermined time,
Communications system. 2. The communication system according to claim 1, wherein the main device is a card reader / writer, and the communication device is a contactless card that communicates with the card reader / writer without contact. 3. A frequency divider for dividing a carrier clock, transmitting means for controlling transmission of transmission data by an output of the frequency divider, receiving means for sampling received data by an output of the frequency divider, A communication device comprising: reset means for resetting the frequency divider when data changes, and for starting the operation of the frequency divider after a lapse of a predetermined time.