NXP Semiconductors K32 L2A Series, Reference Manual, Page: 530 / 1379

The EMV SIM module will generate interrupts once a threshold number of characters is
received. The software should react to these interrupts and read the characters from the
receive FIFO (RX_BUF) until the complete ATR has been received. If a General Purpose
Counter interrupt occurs before the final ATR character is received, then the card should
be deactivated according to the ISO 7816-3 spec (See Section Smart Card Interface and
Control). Otherwise, once a valid ATR is received, the software will know from the ATR
information the specific characteristics for this card (refer to the ISO 7816-3 spec for
details).
21.6.8.1 Programming Considerations for T=0 Smart Cards
If the card is of type T=0, the software should adjust the following parameters according
to the information in the ATR:
• Adjust the baud rate by changing the values of DIVISOR register based on the values
of 'F' and 'D' received in the ATR.
• Adjust the guard time between characters by changing the value of GETU[7:0] in the
TX_GETU register.
• Adjust NACK capability by modifying the values of the ONACK and ANACK bits
in the CTRL register.
• Adjust the stop clock polarity by modifying the value of the SCSP bit in the PCSR
register.
• Adjust the level of transmit NACK re-transmissions allowed by modifying the value
of the TNCK_THD[3:0] bits in the TX_THD register.
• Adjust the level for the Receive NACK threshold by modifying the
RNCK_THD[3:0] bits in the RX_THD register.
If a negotiation with the Smart Card is desired, the software sends a PPS response to the
Smart Card. To send the response, the following steps should be performed:
• Set the desired transmit FIFO threshold level by writing the TDT[3:0] bits in the
TX_THD register.
• Clear all transmit interrupt flags in the TX_STATUS register by writing a one to the
bits of the register.
• Enable the transmit interrupts desired by clearing the mask bits in the INT_MASK
register. If more than 4 characters are to be sent, it is suggested that the TDTF
interrupt be used to signify when to write more characters to the transmit FIFO. This
results in the most efficient transfer times to the Smart Card.
• Enable the transmitter by setting the XMT_EN bit in the CTRL register.
• Write the characters to be sent as response (max 4) to the transmit FIFO using the
TX_BUF register.
Functional Description
K32 L2A Reference Manual, Rev. 2, 01/2020
530 NXP Semiconductors