A subscriber identity module or SIM is a smart card that is designed to fit into mobile phone. It provides the identification of a user to a network, allowing him or her to access such services as telephony, email, internet and text messaging.
The SIM card contains a microcomputer as well as a certain amount of memory to process commands (Random Access Memory or RAM), and to store user files (Electronically Erasable Programmable Read Only Memory or EEPROM). The SIM also contains an amount of Read Only Memory (ROM) which stores the cards operating system.
When the SIM card is activated the microcomputer loads the operating system from ROM into the RAM of the card and processes commands as requested by the mobile equipment (ME) or card access device (CAD).
Smart Card (SIM Card) pinout
|C1||VCC||+5 VDC power supply input (optional use by the card)|
|C2||RESET||Reset signal, used to reset the card’s communications. Either used itself (reset signal supplied from the interface device) or in combination with an interal reset control circuit (optional use by the card). If internal reset is implemented, the voltage supply on Vcc is mandatory|
|C3||CLOCK||Provides the card with a clock signal, from which data communications timing is derived|
|C4||RESERVED||AUX1, optionally used for USB interfaces and other uses.|
|C5||GND||Ground (reference voltage)|
|C6||Vpp||Programing voltage input (optional). This contact may be used to supply the voltage required to program or to erase the internal non-volatile memory. ISO/IEC 7816-3:1997 designated this as a programming voltage: an input for a higher voltage to program persistent memory (e.g., EEPROM). ISO/IEC 7816-3:2006 designates it SPU, for either standard or proprietary use, as input and/or output.|
|C7||I/O||Input or Output for serial data (half-duplex) to the integrated circuit inside the card.|
|C8||RESERVED||AUX2, optionally used for USB interfaces and other uses.|