LM3S818 Luminary Micro, Inc, LM3S818 Datasheet - Page 28

• Manufacturer Part Number: LM3S818
• Description: Lm3s818 Arm Microcontroller
• Manufacturer: Luminary Micro, Inc

Architectural Overview
1.4.4
1.4.4.1
1.4.4.2
1.4.5
1.4.5.1
1.4.5.2
28
Serial Communications Peripherals
The LM3S818 controller supports both asynchronous and synchronous serial communications
with two fully programmable 16C550-type UARTs and SSI serial communications.
UART (Section 12 on page 229)
A Universal Asynchronous Receiver/Transmitter (UART) is an integrated circuit used for RS-232C
serial communications, containing a transmitter (parallel-to-serial converter) and a receiver
(serial-to-parallel converter), each clocked separately.
The LM3S818 controller includes two fully programmable 16C550-type UARTs that support data
transfer speeds up to 460.8 Kbps. (Although similar in functionality to a 16C550 UART, it is not
register compatible.)
Separate 16x8 transmit (TX) and 16x12 receive (RX) FIFOs reduce CPU interrupt service loading.
The UART can generate individually masked interrupts from the RX, TX, modem status, and error
conditions. The module provides a single combined interrupt when any of the interrupts are
asserted and are unmasked.
SSI (Section 13 on page 265)
Synchronous Serial Interface (SSI) is a four-wire bi-directional communications interface.
The Stellaris SSI module provides the functionality for synchronous serial communications with
peripheral devices, and can be configured to use the Freescale SPI, MICROWIRE, or TI
synchronous serial interface frame formats. The size of the data frame is also configurable, and
can be set between 4 and 16 bits, inclusive.
The SSI module performs serial-to-parallel conversion on data received from a peripheral device,
and parallel-to-serial conversion on data transmitted to a peripheral device. The TX and RX paths
are buffered with internal FIFOs, allowing up to eight 16-bit values to be stored independently.
The SSI module can be configured as either a master or slave device. As a slave device, the SSI
module can also be configured to disable its output, which allows a master device to be coupled
with multiple slave devices.
The SSI module also includes a programmable bit rate clock divider and prescaler to generate the
output serial clock derived from the SSI module’s input clock. Bit rates are generated based on the
input clock and the maximum bit rate is determined by the connected peripheral.
System Peripherals
Programmable GPIOs (Section 8 on page 106)
General-purpose input/output (GPIO) pins offer flexibility for a variety of connections.
The Stellaris GPIO module is composed of five physical GPIO blocks, each corresponding to an
individual GPIO port. The GPIO module is FiRM-compliant (compliant to the ARM Foundation IP
for Real-Time Microcontrollers specification) and supports 0 to 30 programmable input/output pins.
The number of GPIOs available depends on the peripherals being used (see Table 18-4 on
page 369 for the signals available to each GPIO pin).
The GPIO module features programmable interrupt generation as either edge-triggered or
level-sensitive on all pins, programmable control for GPIO pad configuration, and bit masking in
both read and write operations through address lines.
Three Programmable Timers (Section 9 on page 144)
Programmable timers can be used to count or time external events that drive the Timer input pins.
Preliminary
February 6, 2007