Figure 13-5. LIN Synchronization Field
0 1 2 3 4 5 6 7 8 9 10 11 12 13
Edge 1 Edge 5
Synch Field
8 Tbit
0 1 2 3 4 5 6 7 8
Sync Break Detect
Sync Break
13.3.8 FIFO Operation
The UART has two 16x8 FIFOs; one for transmit and one for receive. Both FIFOs are accessed via
the UART Data (UARTDR) register (see page 628). Read operations of the UARTDR register return
a 12-bit value consisting of 8 data bits and 4 error flags while write operations place 8-bit data in
the transmit FIFO.
Out of reset, both FIFOs are disabled and act as 1-byte-deep holding registers. The FIFOs are
enabled by setting the FEN bit in UARTLCRH (page 639).
FIFO status can be monitored via the UART Flag (UARTFR) register (see page 633) and the UART
Receive Status (UARTRSR) register. Hardware monitors empty, full and overrun conditions. The
UARTFR register contains empty and full flags (TXFE, TXFF, RXFE, and RXFF bits), and the
UARTRSR register shows overrun status via the OE bit. If the FIFOs are disabled, the empty and
full flags are set according to the status of the 1-byte-deep holding registers.
The trigger points at which the FIFOs generate interrupts is controlled via the UART Interrupt FIFO
Level Select (UARTIFLS) register (see page 645). Both FIFOs can be individually configured to
trigger interrupts at different levels. Available configurations include ⅛, ¼, ½, ¾, and ⅞. For example,
if the ¼ option is selected for the receive FIFO, the UART generates a receive interrupt after 4 data
bytes are received. Out of reset, both FIFOs are configured to trigger an interrupt at the ½ mark.
13.3.9 Interrupts
The UART can generate interrupts when the following conditions are observed:
■ Overrun Error
■ Break Error
■ Parity Error
■ Framing Error
■ Receive Timeout
■ Transmit (when condition defined in the TXIFLSEL bit in the UARTIFLS register is met, or if the
EOT bit in UARTCTL is set, when the last bit of all transmitted data leaves the serializer)
■ Receive (when condition defined in the RXIFLSEL bit in the UARTIFLS register is met)
All of the interrupt events are ORed together before being sent to the interrupt controller, so the
UART can only generate a single interrupt request to the controller at any given time. Software can
623July 24, 2012
Texas Instruments-Production Data
Stellaris
®
LM3S6G65 Microcontroller
OBSOLETE: TI has discontinued production of this device.
