MIFARE Series 2-Non-contact card standard

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Depending on the way the signal is sent and received, Iso/iec14443-3 defines the TypeA, typeb two card types. They differ mainly in the modulation depth of the carrier and the encoding of the binary number. When transmitting a signal from a read-write implement to a card, the two transmit the signal via a 13.56Mhz RF carrier.

TypeA, a representative of Philips and Siemens AG. It sends 100%ask modulated corrected Miller coding, transmission rate 106kb/s; receive-subcarrier modulation 847.5kHz Manchester encoding. Simply put, when the information ' 1 ', the signal will have 0.2-0.3 subtle gap, when the information ' 0 ', the signal may have a gap or not, and before and after the information. The advantage of this method is that the information difference is obvious, the chance of being disturbed is less, the reaction speed is not easy to operate, and the disadvantage is that the energy may fluctuate when it is necessary to continuously increase the energy to the contactless card.

TypeB, a representative of Motorola, STMicroelectronics. It sends 10%ask modulation digital encoding NRZ (non-zeroing), transmission rate 106kb/s, receive-subcarrier modulation 847.5kHz Digital encoding BPSK (binary phase keying) transfer rate 106kb/s. That is, information ' 1 ' and information ' 0 ' is the difference between information ' 1 ' signal amplitude, that is, the signal is strong, information ' 0 ' signal amplitude is small, that is, the signal is weak. The advantage of this way is the continuous signal transmission, there will be no energy fluctuations, the disadvantage is that the information difference is not obvious, relatively susceptible to external interference, will be wrong signal appears, of course, can also be used to make up the test.

The following points can be seen from the comparison of TypeA and TypeB:
1) from the reader to the card modulation, TypeA with 100%ask, so the signal difference is obvious, easy to detect, strong anti-jamming ability; But at each bit of transmission (at a transfer rate of 106kb/s, Transmission period is 9.4μs), there is about 3 of the signal gap μs, then the reader to Card energy supply is interrupted, must be in the card circuit to add a large capacity capacitor to maintain a certain energy supply, and TYPEB with 10%ask, the card can obtain continuous energy from the reader, but the signal difference is not obvious, easy to cause misreading /write, poor anti-jamming ability.
2)the interruption of the TypeA card energy will cause the interrupt of the card clock, while the avoidance of clock interruption may leave a backdoor, allowing "single-step Tracking".
3) when trying to speed up, such as the transfer rate of 212kb/s, the bit transfer period is only 4.7μs, in this case 3μs interrupt is greater than 60% of the transmission period, and the transfer rate is 424kb/s, Bit transfer period is only 2.35μs, in this case 3μs interrupt has made the system can not work, both typea can not achieve this speed transmission, can not speed up!
4)TypeA anti-collision requires higher and more accurate timing on the card, so you need to add some hardware to the card and reader, while the TYPEB conflict prevention can be implemented by software.

From the above comparison, it can be seen that the two technologies are difficult to say, which is one of the reasons why the international ISO organization determines two kinds of standards. However, for the public transport system, it is necessary to carefully analyze, it is best to adopt a standard. On the bus, the interference is very big, the punch-in time must be very fast, so the probability of false signal appears as small as possible, from this aspect, the use of TypeA relatively suitable for some. In addition, due to national conditions, public transport in the short-term use of non-contact CPU card opportunities are not small, generally using contactless logic encryption card. In the use of non-contact logic encryption card process, because the Cary does not have the CPU in the work, the continuity of energy requirements is not very strong, so typea can work very well, this is also TYPEB force push non-contact CPU card reason, they basically do not produce contactless logic encryption card.

MIFARE Series 2-contactless card standard (RPM)