Mifare Series 2-Non-contact card Standard

According to different signal transmission and receiving methods, ISO/IEC14443-3 defines two types of cards: typea and typeB. Their differences mainly lie in the modulation depth of the carrier and the encoding method of the binary number. When transmitting signals from a read/write machine to a card, the two transmit signals through the RF carrier of 13.56mhz.

Typea represented by Philips and Siemens. It sends the miller code with 100% ASK modulation correction, the transmission rate is kb/s, and the Manchester code with 847.5khz modulation by the receiving-sub-carrier. To put it simply, when the information is '1', the signal will have a subtle gap of 0.2-0.3. when the information is '0', the signal may have gaps or none, it is related to the front and back information. The advantage of this method is that there are obvious information differences, there are few opportunities for interference, and the response speed is fast and it is not easy to misoperate. The disadvantage is that when the energy needs to be continuously improved to a non-contact card, energy may fluctuate.

TypeB, represented by Motorola and IFA semiconductor. It sends a 10% ASK modulation digital code NRZ (not normalized) with a transfer rate of kb/s. It receives a-sub-carrier modulation 847.5khz digital code BPSK (Binary Phase keying) with a transfer rate of kb/s. That is, the difference between information '1' and information '0' is that the signal amplitude of Information '1' is large, that is, the signal is strong, and the signal amplitude of Information '0' is small, that is, the signal is weak. The advantage of this method is that continuous signal transmission does not cause fluctuations in energy. The disadvantage is that the information difference is not obvious, and it is relatively easy to be disturbed by the outside world and may lead to incorrect signals, of course, we can also use the inspection method to make up for it.

From the comparison of typea and typeB, we can see the following points:
1)From Reader to card modulation, typea uses 100% ASK, so the signal difference is obvious, easy to detect, strong anti-interference ability; but when each bit is transferred (the transfer rate is kb/s, when the transmission period is 9.4 μs, there is about 3 signal gaps μs. At this time, the energy supply from the reader to the card is interrupted, A large capacity capacitor must be added to the card circuit to maintain a certain amount of energy supply; while typeB uses 10% ASK, cards can obtain sustained energy from the reader; but the signal difference is not obvious, it is easy to cause misunderstanding/writing, and has poor anti-interference ability.
2)If the energy of a typea card is interrupted, the card clock may be interrupted, and a backdoor may be left to avoid the clock interruption problem, so that "one-step tracking" can be used.
3)When trying to speed up, for example, when the transmission rate is 212kb/s, the bit transmission cycle is only 4.7 μs. In this case, the 3 μs interruption is greater than 60% of the transmission cycle, when the transmission rate is kilobytes kb/s, the bit transmission cycle is only 2.35 μs. In this case, the interruption of 3 μs has made the system unable to work, and neither typea can achieve this speed transfer, cannot speed up!
4)The anti-conflict of typea requires a relatively high and accurate timing sequence on the card. Therefore, you need to add hardware to the card and reader separately, while the anti-conflict of typeB can be implemented by software.

 

From the comparison above, we can see that the two technologies are difficult to say that they are superior or inferior, which is one of the reasons why the international ISO organization has determined the two standards. However, for public transit systems, it is best to adopt a standard after careful analysis. In a bus, the interference is very high, and the clock-in time must be very fast. Therefore, the lower the chance of false signals, the better. In this regard, typea is suitable for some applications. In addition, due to national conditions, there is little chance for public transit to use non-contact CPU cards in a short period of time. Generally, non-contact logic encryption cards are used. In the process of using a non-contact logic encryption card, because there is no CPU in the card, the energy continuity requirements are not very strong, so typea can work very well, this is also the reason why typeB pushes non-contact CPU cards. They basically do not produce non-contact logic encryption cards.

 

Mifare Series 2-Non-contact card Standard