Abstract: Introduced briefly Atmel Corporation’s e5561 radio frequency identification circuit’s internal structure and the principle of work, give use U2270B to read/write the radio frequency recognition system’s design method which the base depot integrated circuit and at89C52 micro controller compose. Simultaneously gives it to read/writes the foundation electric circuit diagram and the monolithic integrated circuit system’s design cycle.
Key word: Encryption; Radio frequency recognition; e5561
Introduction
The radio frequency recognition (RFID) is the radio frequency recognition abbreviation, namely carries on recognition processing through the infinite electric wave. The radio frequency recognition system usually by reads the card (microreader) and the responder (card) two parts is composed. Its identification data is saved in the responder electric circuit. The responder is one kind of non-contact card, this card oneself not charged source, when the card carries on microreader’s electromagnetic field scope, then may through the coupling radio wave energy and after the rectification constant voltage obtains the work power source. Thus, under the state of activation, the data which in the card saves then may through the code, the modulation escort to the microreader to realize the recognition.
Atmel Corporation produces the e5561 electric circuit is one kind of encryption radio frequency recognizer (IDIC), it is suitable for the high security situation, its interior has the encryption arithmetical unit. Its main performance is as follows:
* low power, low voltage CMOS IDIC;
* the radio frequency (RF) the scope is 100kHz~150kHz, the typical value is 125kHz;
* contains 320bitEEPROM (to divide 10);
* the position rate is RF/32, RF/64;
* the encryption distinction time is smaller than 10ms;
* has reads programmable/writes the protection function;
* uses Manchester and two two encoding method.
1 internal structure and principle of work
When normal use e5561 only uses the coil 1(coil1) and the coil 2(coil2) and the external connection inductance coil and the capacitor, other pins have not used. Its internal structure diagram as shown in Figure 1. Chip including auto-adapted partial, pretage parts and so on module end, modulator, decoder, memory, encrypted circuit.
When the base depot and the e5561 resonance frequency does not match, its auto-adapted part adjusts e5561 the frequency to cause its and the base depot frequency match, the setting range is 5%. The pretage simulation end (AFE) may use for the power source which produces the electric circuit to need, simultaneously may process and the base depot bidirectional data communication.
In the chip memory is composed of 320 EEPROM, divides into 10, each 32; 0th uses in preserving the basic layout data, 1st - 9th for user data area, but programs freely, 1-4th is the ID code, 5-8th is the dense spoon, under the password pattern, 9th 4-31 uses in depositing the password, 0-3 use in storing the user layout data, otherwise, the 9th corresponding position may also program freely.
The programming voltage provides (18V) by the high-voltage generator. The encrypted circuit AUT64 operational rule encryption reads in e5561 the password, the operation result may read out by the base depot, compares this result and the base depot data, then may establish the high security the authentication process.
The modulator is composed of 2 data encoders, the basic modulation type has Manchester and two encoding method.
e5561 may work in the below working pattern:
(1) ID pattern: In the RF field, e5561 transmits the ID code to the base depot circulation. The ID pattern permission uses two kind of different positions rate and the modulation system, and may use two kind of lengths the ID code generations (64 or 128).
(2) programs the pattern: Before the use, must carry on the programming to e5561. EEPROM will be divided into 10, each block is programmed separately, the base depot will send out the data series should read in e5561 the EEPROM memory. In programming period, if the e5561 monitoring device discovered that the mistake or the protection are invaded, that the system will return to the ID pattern.
(3) direct access pattern: When the base depot transmits special data series for e5561, e5561 will enter the direct access pattern. This kind of pattern has two kind of functions: First, the base depot reads EEPROM each content; second, again equipment e5561. , If the e5561 monitoring device discovered that the mistake or the protection are invaded, that the system will return to the ID pattern.
(4) encrypts the pattern: In this pattern, e5561 uses the AUT64 operational rule (one kind of misalignment high security operational rule). In the base depot completes after the e5561 recognition (through reads the ID code), the base depot may carry on the distinction to the responder (through to transmit a password), when after receiving this data series, e5561 enters the encryption pattern. If the e5561 monitoring device discovered that the mistake or the protection are invaded, the system will also return to the ID pattern.
(5) stops the pattern: When two or two above responders simultaneously use, is avoids conflicting, the base depot will transmit special data series to cause to be at the initiative condition the responder to enter the stop pattern, afterward through adds the electricity replacement or sends out restarts the order, causes e5561 to enter the ID pattern again.
Between various patterns’ transformation may transmit a sequence order through the base depot to change.
When use, e5561 may receive through the external connection LC return route reads/writes the base depot the RF signal, and provides the power source after electric circuit internal power circuit processing for the electric circuit. The electric circuit may read through the internal damping load the internal EEPROM in data read-in/writes the base depot, and interrupts the RF field by a special way, causes to read/writes the base depot to be possible to read in the data in internal EEPROM.
The base depot after completing the password and the ID code recognition as well as the password distinction, then may have the control signal control system’s movement. Its responder electric circuit as shown in Figure 2.
The responder and the base depot correspondence has two transmission paths: First, the energy transfer channel, another is the signaling channel. The energy transfer channel is unidirectional, may produce by the base depot to the responder power supply electromagnetic field. The signaling channel is bidirectional, usually is “writes” by the base depot to the responder transmission’s information, the reversed direction is “reads” the user data (including user password, the ID code, password and so on). When use, the user may according to need to carry on the programming. Table 1 and Table 2 give EEPROM 0th separately (altogether 32) and the 9th layout data position.
Table 1 0th position meaning and establishment
| Position | Code number | Meaning |
Supposing Setting at Value |
| 0 | MOD | Modulation type | 0: Manchester; 1: Two phase |
| 1 | BR | Position rate | 0:RF/32; 1:RF/64 |
| 2 | BC | Word length | 0:128 bit; 1:64bit |
| 3-4 | T | Terminal | 00: Test; 1 0,0 1: Terminal; 1 1: Does not have |
| 5 | S | Stop pattern | 0: Pass; 1: Opening |
| 6 | A | Auto-adapted part | 0: Automatic; 1: Manual establishment |
| 7 | AUT | Number of times | 0:8 time; 1:24 time |
| 8 | L_0 | The 0th locking | 0: Unlocking; 1: Locking |
| 9-11 | Adapt bit | Fixed | 1; 1; 1 |
| 12-31 | SID | Manufacturer chip code | Leaving the plant hypothesis |
Table 2 9th position meanings and establishment
| Position | Code number | Meaning | Establishment value |
| 0 | L_ID | The 1-4th locking | 0: Unlocking; 1: Locking |
| 1 | L_K | The 5-8th locking | 0: Unlocking; 1: Locking |
| 2 | L_9 | The 9th locking | 0: Xie Xiao; 1: Locking |
| 3 | PWD | Password permission | 0: Permission; 1: Does not permit |
| 4-31 | Depositing password | Programmable establishment |
2 e5561 applications
A basic radio frequency recognition system is usually composed of three normal components: The responder, reads/writes the base depot and the micro controller. Responder electric circuit as shown in Figure which is composed of e5561 2, in the chart gives the inductance coil and the capacitor parameter, this electric circuit’s RF operating frequency is 125kHz.
2.1 read/writes the base depot
The read-write base depot is mainly composed of the U2270B necessary electric circuit. U2270B is IDIC which Atmel Corporation produces reads/writes the base depot allocated-use circuit, its interior includes one by the piece on the power source, the oscillator and the coil actuator is composed, may can become for the responder power supply energy conversion electric circuit and the small input signal the micro controller to need the signal the signal processing electric circuit. It belongs must programs the electric circuit, uses the 5V single power source power supply, the peripheral circuit is quite simple, only need dispose the read-write antenna (L), the resonant capacitor (C), to input the capacitor (CIN) and so on parts then to work. In the antenna carrier frequency is 125kHz, the bit rate is in the RF/32 typical situation, the base depot antenna L inductance quantity is 737μH. Generally uses the copper system lacquer wire to make the diameter is 3cm, the number of windings is 100 coils then.
The radio-frequency carrier permission/forbids the end (CFE) and reads the data out-port (OUTPUT) the foreign connection, should separately and P1.1 is connected with monolithic integrated circuit’s two I/O mouth line P1.0 uses for to carry on the data read-write to the e5561 card.
2.2 monolithic integrated circuit systems
This system’s monolithic integrated circuit uses at890C52 type, its interior has 8KB Flash the EEPROM memory system procedure, mainly uses in completing the keyboard scanning, the demonstration correlation data, the data to carry on read-write processing through U2270B to the card, as well as carries on functions and so on data communication with the superior management main engine. After expansion data-carrier storage AT29C256 Flash EEPROM mainly uses in the power failure data storage. The monolithic integrated circuit and the superior manage main engine’s correspondence to select the RS-485 main line standard, this standard has the connection simple (only to need 2 data lines and 1 grounding), driving force is big, signal distance long (longest 112km), antijamming ability strong and so on characteristics. Because the common microcomputer serial port uses is the RS-232 connection, must therefore match in addition meets the RS-232/RS-485 switch. Reads/writes base depot electric circuit as shown in Figure 3.
Shown in Figure 4 is this system’s monolithic integrated circuit system master routine diagram. In this system, because U2270B can only complete the radio frequency modulation signal and the rectification and the launch, but to chooses the encoding method as well as reads the data stream the decoding, to write the data stream the code and so on to need the software to realize. Generally to make the data easy to decode, when design selects the synchronized signal. As a result of reads the signal the profile along with the modulation, the encoding method difference and the difference, therefore, reads the card procedure to select the simulated signal succession, namely examines the synchronized signal first in the P1.1 mouth, then the basis elects the encoding method carries on the corresponding decoding. The method is to the signal time which and the distinction receives. Writes the card is comes through P1.0 to the U2270B carrier permission/to forbid the end to carry on the control, whether there is by the timed control carrier, its everybody’s order should pay attention with reads when the card, prevents the data byte or a bit confusion.
