SLAU723A October 2017 – October 2018 MSP432E401Y , MSP432E411Y
The UART offers basic support to allow communication with an ISO 7816 smartcard. When bit 3 (SMART) of the UARTCTL register is set, the UnTx signal is used as a bit clock, and the UnRx signal is used as the half-duplex communication line connected to the smartcard. A GPIO signal can be used to generate the reset signal to the smartcard. The remaining smartcard signals should be provided by the system design. The maximum clock rate in this mode is system clock / 16.
When using ISO 7816 mode, the UARTLCRH register must be set to transmit 8-bit words (WLEN bits 6:5 configured to 0x3) with EVEN parity (PEN set and EPS set). In this mode, the UART automatically uses two stop bits, and the STP2 bit of the UARTLCRH register is ignored.
If a parity error is detected during transmission, UnRx is pulled Low during the second stop bit. In this case, the UART aborts the transmission, flushes the transmit FIFO and discards any data it contains, and raises a parity error interrupt, allowing software to detect the problem and initiate retransmission of the affected data. Note that the UART does not support automatic retransmission in this case.