After reset, the Smart Card Interface is disabled. When the Smart Card Interface is enabled, it generates a CARDIN interrupt if it detects that a card has been inserted. Before a card is activated, the interface must be configured to the correct settings for processing the Answer To Reset (ATR) and switched to receive mode.

The card activation sequence is initiated by writing to the STARTUP bit of the SMICTRL register. After the contact activation sequence is complete, the card issues its ATR.

When the first characters of the ATR stream arrive, the interface generates an RXREAD interrupt. The initial character is then read from the interface and used to configure the convention of the interface (direct or inverse) by setting the SMCONV register.

The rest of the ATR sequence is read in and used to configure:

to be used in subsequent communication.

In normal operation, the interface reads and writes blocks of characters to the card. The direction of the data flow is determined by the MODE bit in the SMITCTRL (Integrated Circuit Card Control) register. When the transaction is complete, the card is deactivated by writing to the FINISH bit of the SMICTRL register. If the card is removed prematurely, this is detected by the interface, and the card deactivates automatically.