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DEVELOPING A USB SMARTCARD READER WITH ST7SCR

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unsigned int CRD_EndTransmit(void)

This function finishes the transmission by disabling the interrupt. This function returns the re-

maining number of bytes to be transmitted.

3.3 INTERRUPT FUNCTIONS

The following two functions are executed when an interrupt occurs:

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void INT_UART(void)

This function is used for all CRD interrupts: parity, receive, transmit, waitingtime,

voltage_error, over_current and transmit_empty.

– PARITY: A flag is set if 4 automatic retries have failed.

– WAITINGTIME: A flag is set when a counter overflow is detected.

– VOLTAGE and CURRENT: The corresponding flags are set, the corresponding interrupt is

– TRANSMIT: The transmit register is loaded with the next byte to be sent. If the last byte is

sent, the interrupt is disabled and a flag is set.

– RECEIVE: This function uses a Protocol Type Flag (software) to identify the received bytes

and manage the T=0 and the T=1 special cases.

– TRANSMITEMPTY: Not used.

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void INT_CARDDET(void)

This function will set a flag with Rebound Management (see the Time Base Unit (TBU) func-

tion).

3.4 ICC FUNCTIONS

The following functions execute a global action on the ICC.

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unsigned char ICC_PowerOnAsync(unsigned char Voltage)

This function executes the Power-on sequence in compliance with ISO 7816 specifications for

Card voltage is either 1.8 volts, 3.0 volts or 5.0 volts depending on the value of the Voltage

variable:

– CRD_Voltage18V (for 1.8 volts)

– CRD_Voltage3V (for 3.0 volts)

– CRD_Voltage5V (for 5.0 volts)

This function returns one of the following error codes: