Production and specification of smart cards

Today, the magnetic stripe no longer guarantees the necessary level of protection of information from forgery. Therefore, manufacturers began to produce cards with a chip, which are very often called smart cards. Smart cards can perform various data processing operations. The main advantage of smart cards is their reliability, security and extensive functionality, and the disadvantage is the relatively high cost. The cost of smart cards is determined by the price of the chip, depending on the size of the internal memory and for a circulation of 1 million cards ranges from 0.5 to 8.0 dollars.

Smart Card Chip Sizes
The size of a chip with an integrated circuit significantly affects its fragility. The larger the chip area, the easier it is to break it when the card with the chip is subjected to bending. For example, a smart card with a chip carried in a wallet is subject to large random deformations. Accordingly, the bending stresses of the card and the chip embedded in this card are very large. The tiniest crack in the chip is enough to make the chip useless.

Therefore, most card manufacturers adhere to the upper limit of the chip area, equal to about 25 mm2, and to minimize the risk of chip fracture, its layout tends to be as close as possible to a square one. For example, for one of our Customers, who produces shower cabins of various sizes and functionality, we have implemented an access control system in the warehouse premises of the enterprise based on 4 readers and smart cards, which restricts access to some warehouse premises and records all entrances/exits of service personnel. Smart cards have different capacities, and the memory capacity of a standard smart card is 256 bytes, although smart cards with memory from 32 bytes to 8 KB are available, which allows you to store various necessary information in memory in addition to identification data.

Cost of smart cards
The area occupied by an integrated circuit on the surface of a silicon crystal is one of the decisive factors determining the cost of a chip. For complex and correspondingly more expensive modules, chips are produced that occupy a large area. Many microcontrollers available on the market include features that are not needed in smart cards. Since the implementation of these functions requires additional space on the chip, they can be removed from chips designed for smart cards. Although such attempts to minimize the size of the chip only slightly reduce the cost of a single chip, however, a small saving on a single chip gives a serious profit when producing a large number of them.

Smart Card I/O Channel

Two interface lines are used for I/O traffic between the card and the reader. One of them, the I/O line, transmits bits of data. This line can be in one of two states, one representing 0 and the other 1. The second line, the clock line, indicates when to sample the I/O line to get the data bit.

The smart card I/O channel is a serial channel that operates in half-duplex mode. This means that it transmits data bitwise, in chunks, and 1 byte at a time, and the data stream can only go in one direction at any given time. If both the terminal and the card transmit data at the same time, the data will be lost. If they go into receive mode at the same time, the system will go into a mutual lock state. Therefore, the actions of the smart card and the terminal must be synchronized.

Each side of the communication channel must monitor whether the exchange partner is in the transmit state or in the receive state. If an undefined situation occurs as a result of an exchange of erroneous messages, then the reader is responsible for restarting the entire sequence of the exchange protocol to prevent a channel failure. As an example of a working system based on smart cards, we can cite the project of an automated access control system for warehouses implemented by our company for the company “Meridian Stroy”, which produces stamped and stamped anti-corrosion tees for main oil and gas pipelines, while the system uses six RFID readers from Motorola.

The communication protocol between the host computer and the smart card supports the master (host-computer) relationship.) and the slave (smart card). The host computer sends commands to the card and listens for the response. The smart card never sends data to the host computer except in response to its command. Smart card operating systems typically support both character-by-character and block-by-block exchanges. The smart card hardware can process data at 115,200 bps, but most smart card terminals typically communicate with cards at speeds significantly lower than this, in particular managing contact smart cards at 9,600 bps, and contactless smart cards at 7800 bps.

Moving towards more advanced I/O mechanisms is one of the areas of development of smart card technology. Some new smart cards allow direct use of the USB channel. The USB interface uses two additional lines to form a second I/O channel. This is achieved by a full-duplex connection. The USB channel operates in duplex mode with increased speed. At higher speeds, existing smart card operating system architectures can also work.

An important step in improving the I/O channel of a smart card is the introduction of hardware support for data transmission. Until now, the reception and transmission of data through the smart card interface was controlled exclusively by the software of the operating system without any hardware support. This greatly complicates the software, and also increases the possibility of software errors. However, the main problem is the speed limit of the software-supported data transfer, since the processor speed itself is strictly limited.

To offload the processor and get higher communication speeds, a universal asynchronous receiving and transmitting unit UART (Universal Asynchronous Receiver Transmitter) has been developed. This block allows you to receive and transmit data without directly involving the processor in these actions. It is not limited to processor performance and does not need software for byte-level communication. Of course, the higher levels of the data transfer protocol must be represented in the smart card as software, but the lowest level is implemented as software in the UART. Currently, only a limited number of microcontrollers provide hardware support for communications using UART. In future smart card microcontrollers, the use of UART is likely to become the standard.