LM3S600-IQN20-A0T Bookham Technology, Inc., LM3S600-IQN20-A0T Datasheet - Page 220

• Manufacturer Part Number: LM3S600-IQN20-A0T
• Description: Microcontroller
• Manufacturer: Bookham Technology, Inc.

Universal Asynchronous Receivers/Transmitters (UARTs)
11.2.6
11.3
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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
service multiple interrupt events in a single interrupt service routine by reading the UART Masked
Interrupt Status (UARTMIS) register (see page 239).
The interrupt events that can trigger a controller-level interrupt are defined in the UART Interrupt
Mask (UARTIM ) register (see page 236) by setting the corresponding IM bit to 1. If interrupts are
not used, the raw interrupt status is always visible via the UART Raw Interrupt Status (UARTRIS)
register (see page 238).
Interrupts are always cleared (for both the UARTMIS and UARTRIS registers) by setting the
corresponding bit in the UART Interrupt Clear (UARTICR) register (see page 240).
The receive timeout interrupt is asserted when the receive FIFO is not empty, and no further data
is received over a 32-bit period. The receive timeout interrupt is cleared either when the FIFO
becomes empty through reading all the data (or by reading the holding register), or when a 1 is
written to the corresponding bit in the UARTICR register.
Loopback Operation
The UART can be placed into an internal loopback mode for diagnostic or debug work. This is
accomplished by setting the LBE bit in the UARTCTL register (see page 233). In loopback mode,
data transmitted on UnTx is received on the UnRx input.
Initialization and Configuration
To use the UARTs, the peripheral clock must be enabled by setting the UART0 or UART1 bits in the
RCGC1 register.
This section discusses the steps that are required for using a UART module. For this example, the
system clock is assumed to be 20 MHz and the desired UART configuration is:
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The first thing to consider when programming the UART is the baud-rate divisor (BRD), since the
UARTIBRD and UARTFBRD registers must be written before the UARTLCRH register. Using the
equation described in “Baud-Rate Generation” on page 218, the BRD can be calculated:
Parity Error
Framing Error
Receive Timeout
Transmit (when condition defined in the TXIFLSEL bit in the UARTIFLS register is met)
Receive (when condition defined in the RXIFLSEL bit in the UARTIFLS register is met)
115200 baud rate
Data length of 8 bits
One stop bit
No parity
FIFOs disabled
No interrupts
Preliminary
October 01, 2007