SNIU028D February 2016 – September 2020 UCD3138 , UCD3138064 , UCD3138064A , UCD3138128 , UCD3138A , UCD3138A64
The UCD3138’s UART module provides hardware indication of error conditions to provide information about the status of module operation. According to the data being assembled by the receiver, the UART monitors the data received for errors and sets the parity error (PE), framing error (FE), and/or the break-detect (BRKDT) flag when these conditions are detected.
In addition, the UART sets the overrun error (OE) flag if a transfer of new data from UARTRXSHF to UARTRXBUF overwrites unread data in UARTRXBUF. (If both overrun and parity errors occur, only the overrun error flag is set.)
The UART sets the wake-up flag (WAKEUP) if bus activity on the RX line either prevents power-down mode from being entered, or RX line activity causes an exit from power-down mode. Each of these flags is located in the receiver status (UARTRXST) register.
The RXERR flag, also in the UARTRXST register, is the logical OR of the parity error, framing error, overrun error, wake-up, and break-detect flags.
This UART Data Transfer feature allows software that is polling for receiver errors to check only one bit, which will indicate if any or all of the five error conditions are active.
Error interrupts are controlled by three separate enable bits: RXERR_INT_ENA, BRKDT_INT_ENA, and WAKEUP_INT_ENA.
If RXERR_INT_ENA (UARTCTRL3.0) is set, an error interrupt is generated when the receiver detects either a parity, framing, or overrun error. The break-detect interrupt is enabled separately.
If BRKDT_INT_ENA (UARTCTRL3.1) is set, an error interrupt is generated if the receiver detects a break condition. A break condition occurs when the SCI_RX line remains continuously low (active) for at least 10 bits immediately following a missed stop bit.
If WAKEUP_INT_ENA (UARTCTRL3.2) is set, an error interrupt is generated when bus activity on the RX line either prevents power-down mode from being entered or RX line activity causes an exit from power-down mode.