SPRUJF2A March 2026 – March 2026 AM13E23019
ISO7816 Smart Card support is only available for Basic UNICOMM-UART instances.
The UNICOMM-UART Smart Card support feature enables basic communication with an ISO7816 smart card. When configuring the CTL0.MODE field, select the smart card option, the TXD signal is used as a bit clock, and the RXD signal is used as the half-duplex communication line connected to the smart card. Further smart card signals are not supported by UNICOMM-UART.
The clock rate of the UART clock in ISO7816 mode must be in the range of 1 MHz to 5 MHz when using ISO7816 mode, the LCRH register must be set to:In ISO7816 mode, the UART automatically uses 2 stop bits and oversampling of 16 is used; LCRH.STP2 & CTL0.HSE bits are ignored.
If a parity error is detected during a transmission, the RX line is pulled low during the second stop bit. In this case, the UNICOMM-UART aborts the transmission and flushes the TX FIFO. Additionally,the module raises a parity error interrupt, allowing the software to detect the problem and initiate retransmission of the affected data, as the UART does not support automatic retransmission in this case. The UART does not support automatic retransmission on parity errors. If a parity error is detected on transmission, all further transmit operations are aborted and software must handle retransmission of the affected byte or message.
In Smartcard Mode, the receiver in case of parity error drives the line low and a parity interrupt flag is asserted. The transmitter responds based on the value of this bit.