Summary: The radio frequency of low end that AT88RF020 is 13.56MHz discerns the card, follow ISO/IEC 14443 Type B agreement. Introduce the intersection of Model AT88RF020 and the intersection of radio frequency and characteristic, operation principle of card and have dinner application manage, in school emphatically, provide some procedure codes at the same time.
Keyword: The radio frequency is discerned; AT88RF020; Media reader; Have dinner to manage
A foreword
Nowadays, when have dinner and compare university, junior college and special secondary school and middle school concentrated in some, having dinner basically adopts the computer to manage. Students can be consumed in the dining room of the school conveniently according to a non- contact-type RFID card. Some schools have adopted the all-purpose card of the campus, so long as hold the legal RFID card, can consume in the public consumption place within the range of whole school.
RFID is a abbreviation of Radio Frequency Identification, the radio frequency discerns card or reaction type electronic circuit,etc.. RFID radio frequency discerns it is the non- contact-type automatic recognition technology, it discerns the target target and obtains the relevant data automatically through the radio frequency signal, discern the work does not need manual intervention, can work in various abominable environments. RFID technology can discern the high-speed body in motion and can discern a plurality of labels at the same time, operation is swift and convenient. The circuit of Model AT88RF020 is the non- contact-type RFID card that Atmel Company produces.
Characteristic of 2 AT88RF020
The radio frequency of the Model AT88RF020 discerns the main characteristic of the card as follows:
13.56MHz radio frequency card, follow ISO/ECl4443 Type B agreement;
The capacity is a 2048 bytes;
Each card has only sequence number;
Encrypt and lock the function;
There are 1 and once sex counter;
All the intersection of transmission and including one byte the intersection of circulation and the intersection of check-up and yard under information;
Write time is 3ms;
Write the number of times is 100 000 times;
The temperature range of working environment is 0 ℃ and a 70 ℃.
Composition and operation principle of the recognition system of radio frequency 3
3. Basic composition of 1 RFID system
1Label Tag, namely radio frequency card
Made up of coupling component and circuit, the label contains the built-in aerial, used for carrying on communication with the radio frequency aerial, each label has the only electronic code, affix to object and annotate the target target. Fig. 1 shows the internal structure of Model AT88RF020 RFID.
2Reader Reader or media reader
Read can also write into besides reading the card The apparatus of label information, can be designed the holding type or fixed type.
3Aerial Antenna
In the label radio frequency card With transmitting the radio frequency signal between the media readers. The intersection of location and the intersection of plane and main system at some system pass RS232 or the intersection of RS485 and interface and external computer of media reader still ‘ Connect, carry on data interchange.
3. Basic operation principle of 2 RFID system
The basic operation principle of RFID system is that the media reader sends certain frequency such as 13.56MHz through launching the aerial , the radio frequency card obtains energy and is activated; Information, through the disposing and launching the aerial to send out of radio frequency card that the radio frequency card encodes being one’s own,etc.; The systematic reception antenna receive the signal carrier signal sent from the radio frequency card, convey to the media reader by the regulator of the aerial, send backstage supporter’s main system to carry on relevantly and deal with after carrying on demodulation and decoding to the signal received with media reader; The main system judges the legitimacy that should be nipped according to logic operation, makes corresponding treatment and control to different settlement, send out the order signal, control the movements of executive body.
3. Structure and operation principle of 3 RFID systematic media reader
As to media reader, in coupling way electromagnetic such as the inductance , communication procedure such as FDX, HDX, SEQ The intersection of radio frequency and the intersection of card and the intersection of data and transmission means such as support modulate, scatter, high times of harmonic wave backward to get media reader And respects such as frequency range,etc., different contacting and transmitting the method although have basic differences, but all media readers are very similar on the function principle and on the design structure decided by this, all readers can be simplified for 2 pieces of basic module of high-frequency interface and control unit. The high-frequency interface includes telephone transmitter and receiver, its function includes producing high frequency and launching the power in order to start the radio frequency card and offer energy; Pay modulating in transmitting signals, is used for conveying the data to the radio frequency card; Receive and demodulate the high-frequency signal from radio frequency card. It has some differences that the high-frequency interface of different radio frequency recognition systems is designed, the inductance couples the high-frequency interface principle of the system.
The function of the media reader control unit includes and employs the system software to carry on communication and carry out the order employing the system software to send; Control the communication course with the radio frequency card mainly from the principle ; Compiled code of the signal. Still carry out and collide with the algorithm to some special systems instead, encrypt and decipher the data to be conveyed among radio frequency card and reader, and such additional functions as the identity carried on among radio frequency card and media reader is verified.
Memory structure of 4 AT88RF020
AT88RF020 has memory capacity of the 2048 bytes, divided into page 32, 8 bytes of page each, store the structure and is shown in Table 1.
The above table wins a bid to have ” One ” Byte define at be dispatched from the factory let user for O in values initial.
Pseudo Unique PICC ID is the only sequence number of the card; The sequence number of the card is written into by the manufacturer, can’t revise.
Application Data employs the data, a part that this data reply information as ATQB transmits in the reading and writing device from the card.
Counter is a counter, carries out a COtJNT order each time, the value of the counter adds l, the initial value is presumed it is 0 by the producer.
Signature signs used for encrypting ,Data this lie in one byte in front of pages 2, can be through COUNT instruction modification, Countex and Signature can offer further safe protection.
Password is a password, put in page 3, can’t read.
Lock Bits locks the location, lies in page 0, prove that can order to revise LOCK, lock every one in the location and correspond to page every of the memory after the password, if some are set as ” 1″ ,The corresponding page is locked very much, can’t write any more, there is no mechanism to unblock, so once page some is locked, its content can’t be revised again, it is 0 to dispatch from the factory the initial value.
Daily order and function of 5 AT88RF020
5. Daily order of 1 AT88RF020
1REQB/ WUPB
This order is used for seeking the card or waking the card in HALT state up, this kind of card only responds to and employs codes API It is a situation of 00 or 01, if receive WUPB with invalid API code to order, it is in HALT state to still nip.
2ATTRIB
This order is used for selecting a card from card of all responses REQB/ WUPB, hereafter, the card entered ACTVE state.
3Slot MARKER
This order offers the card used for inquiring the random number is greater than 1 for reading and writing device.
4HALTB
This ordered to set up the card in HALT state, can only carry out WUPB to order hereafter.
5READ
READ is used for reading the data in the card. Read page 0, 1, 2 needn’t verify the password, but the data of page 3 can’t be read, can only order to be revised through PASSWORD. Other pages prove that can be read after the password.
6WRITE
This orders to be used for writing the card into the data.
7LOCK
This order could be carried out after verifying the password only, is used for locking a certain address area, the address area locked can be read after proving the password.
8CHECK PASSWORD
The check-up of password is ordered, carry out after the apparatus enters ready state.
9DESELECT
Not about card that is in ACTIVE state and through,then last correct answer information card, and enter HALT state.
10COUNT
This order is used for writing page 2. COUNT data not brought write the previous 6 bytes of page 2 into in the order, back 2 bytes use by counter, carry out COUNT once to order each time, the value of the counter is added by 1, the value of the counter is up to 215 o’clock, can’t carry out COUNT operation any more, and page 2 is locked, can’t revise any more. Carrying out should verify the password before this order. Having the electricity or starting the workflow again of AT88RF020.
5. Function of 2 AT88RF020
With rf_attrib as follows ‘ The function is that an example explains the usage of the function of AT88RF020.
1Function rf_attrib Form
Int rf_attrib HANDLE icdev, unsigned long pupi, unsigned char param, unsigned clam eid, unsigned char brTx, unsigned char brRx ;
2Function of the function
Choose a card from already responding to the card that REQB/ WUPB has ordered, distribute a ID number for each card at the same time.
3The parameter of the function is described
icdev: rf_init The apparatus returning describes incantations
pupi: Pseudo-Unique PICC Identifier
param: Set as O
cid: Card ID number O-15 ,Operation behind this value is stored and supported in the card
brTx: By PCD near the coupling apparatus To PICC near the coupling integrated circuit card Potter rate. As to AT88RF020, 0×00 represents 106Kbit/ s
brRx: Potter rate from PICC to PCD. As to AT88RF020, Ox00 represents 106Kbit/ s
4Returning value: =0: Succeed
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