As illustrated in Figure 2, today’s smart card controller typically includes an 8-bit CPU, 128–780 bytes of RAM, 4–20 KB of ROM, 1–16 KB of EEPROM on a single die, and (optionally) an on-chip hardware encryption module.

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Figure 2—At a minimum, the standard smartcard microcontroller contains a CPU and blocks of memory including RAM, ROM, and some sort of nonvolatile memory (usually EEPROM).

The EEPROM is ideal for this application since the stored data usually changes over the card’s lifetime or is unique to the card, such as a card identification number, a PIN (personal identification number), authorization levels, cash balances, credit limits, and so on.

This year, improvements to the controller include advanced RISC cores and increases in memory sizes to 32 KB of ROM or EEPROM.

Memory-management units are included on devices that support multiapplication cards. Encryption and decryption hardware accelerators support additional algorithms with 1024 and larger key lengths.

Although it functions like a typical micro with instruction-set compatibility, the smart-card controller is fundamentally different because it’s primarily designed for security. For instance, if you compare smart cards using the Motorola 68HC05 with its nonsmart-card Motorola counterparts, several differences become clear.

Most obvious is the smart card’s single memory-mapped I/O. There are only five standard ISO-defined pinouts on a smart card: I/O, Clock, Power, Ground, Reset.

The smart card uses only onboard memory with relatively large amounts of nonvolatile memory. EEPROM programming is accomplished by an on-chip charge pump so it is controlled by the CPU and not accessible directly by external command. It appears stripped down compared to a nonsmart-card device since it contains no additional peripherals (e.g., ADC, PWMs, serial or parallel interfaces).

To increase mechanical robustness, smart-card devices are constrained by die size and use very dense memory elements. Devices for contactless cards use a microcontroller with analog circuitry that conditions the data and information transmitted over the interface. The card includes capacitive plates or a coil for coupling with the reader (see Figure 3).

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Figure 3—Devices for contactless cards involed a microcontroller with analog circuitry that conditions the data and information transmitted over the interface while the card includes capacitive plates or a coil for coupling with the reader.