Figure 1: ISO ID 1Card
The Contact Card is the most commonly seen ICC to date largely because of its use in France and now other parts of Europe as a telephone prepayment card.. Most contact cards contain a simple integrated circuit although various experiments have taken place using two chips. The chip itself varies considerably between different manufacturers and for a whole gambit of applications. Let us consider first the purpose for the 6 contacts used by the ICC (fig 2)
Figure 2: ISO 7816-2 Connector Vcc is the supply voltage that drives the chips and is generally 5 volts. It should be noted however that in the future we are likely to see a move towards 3 volts taking advantage of advanced semiconductor technology and allowing much lower current levels to be consumed by the integrated circuit. Vss is the substrate or ground reference voltage against which the Vcc potential is measured. Reset is the signal line that is used to initiate the state of the integrated circuit after power on.This is in itself an integral and complex process that we shall describe later in more detail. The clock signal is used drive the logic of the IC and is also used as the reference for the serial communications link. There are two commonly used clock speeds 3.57 MHZ and 4.92 MHZ. The lower speed is most commonly used to date in Europe but this may change in the future. One may be tempted to ask why these strange frequencies were chosen, why not just a straight 5 MHZ. The reason lies in the availability of cheap crystals to form the clock oscillator circuits. Both of these frequencies are used in the television world for the colour sub carrier frequency. The PAL system operates using 4.92 MHZ whilst the 3.57 MHZ is used by the American NTSC standard. The the Vpp connector is used for the high voltage signal that is necessary to program the EPROM memory. Last, but by no means least is the serial input/output (SIO) connector. This is the signal line by which the chip receives commands and interchanges data with the outside world. This is also a fairly complex operation and will be the subject of a more detailed discussion where symbols such as T0 and T1 will be fully explained. So what does the chip contain, well the primary use of the IC card is for the portable storage and retrieval of data. Hence the fundamental component of the IC is a memory module. The following list represents the more commonly used memory types,
T ROM T PROM T EPROM T EEPROM T RAM
Read only memory (mask ROM) Programmable read only memory Erasable programmable ROM Electrically erasable PROM Random access memory
A particular chip may have one or more of these memory types. These memory types have particular...