6/14

DEVELOPING A USB SMARTCARD READER WITH ST7SCR

2 IFD IMPLEMENTATION

The Interface Device (IFD) implementation firmware contains one file:

– Ifd_protocol.c: This is the ISO 7816 implementation for Protocol types T=0 and T=1 and for

character, TPDU and short APDU levels.

The protocol type is also managed at the CRD level by the interrupt system for data reception

from the ICC. For this release, only the T=0 with character level has been implemented in the

current firmware.

This part has to be modified in depth to integrate the secure function and other communication

types and levels.

All the functions in this part are called by a CCID function. These functions are typically those

where the reader interprets the messages sent to/from the ICC and manages the parameters

for ICC communication (speed, type, etc....).

An IFD structure is used to save all the current parameters in compliance with CCID specifi-

cations.

The following functions are used for ICC and parameter management:

– IFD_Init(): This sets the parameter structure to the default value.

– IFD_GetParameters(): This returns the current parameters in a buffer.

– IFD_SetParameters(): This enters the new parameters in the IFD structure and programs

the CRD for use with the new configuration.

– IFD_ApplyParametersStructure(): This programs the CRD to use the configuration de-

scribed by the IFD structure.

– IFD_UpdateConvParameterStructure(): This changes the convention parameter of the

structure with the value programmed in the CRD.

turns the Answer to Reset (ATR) variable.

– IFD_XfrBlock(): This sends a command and receives the answer with current parameters.

– IFD_XfrCharT0(): This is given by the IFD structure. (Character level and T=0 type).

– IFD_Escape(): This is dedicated to specific communication between reader and PC. (see

CCID spec).

– IFD_SetClock(): This changes the clock state as configured in the IFD structure.