LM3S2939 Datasheet, PDF (50/749 Pages) Texas Instruments – Stellaris® LM3S2939 Microcontroller

Architectural Overview
1.4.4.4
1.4.5
1.4.5.1
1.4.5.2
1.4.5.3
Both the I²C master and slave can generate interrupts. The I²C master generates interrupts when
a transmit or receive operation completes (or aborts due to an error). The I²C slave generates
interrupts when data has been sent or requested by a master.
Controller Area Network (see page 549)
Controller Area Network (CAN) is a multicast shared serial-bus standard for connecting electronic
control units (ECUs). CAN was specifically designed to be robust in electromagnetically noisy
environments and can utilize a differential balanced line like RS-485 or a more robust twisted-pair
wire. Originally created for automotive purposes, now it is used in many embedded control
applications (for example, industrial or medical). Bit rates up to 1Mb/s are possible at network lengths
below 40 meters. Decreased bit rates allow longer network distances (for example, 125 Kb/s at
500m).
A transmitter sends a message to all CAN nodes (broadcasting). Each node decides on the basis
of the identifier received whether it should process the message. The identifier also determines the
priority that the message enjoys in competition for bus access. Each CAN message can transmit
from 0 to 8 bytes of user information. The LM3S2939 includes one CAN unit.
System Peripherals
Programmable GPIOs (see page 285)
General-purpose input/output (GPIO) pins offer flexibility for a variety of connections.
The Stellaris GPIO module is comprised of eight 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 18-57 programmable input/output pins.
The number of GPIOs available depends on the peripherals being used (see “Signal
Tables” on page 667 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. Pins configured as digital inputs are
Schmitt-triggered.
Three Programmable Timers (see page 334)
Programmable timers can be used to count or time external events that drive the Timer input pins.
The Stellaris General-Purpose Timer Module (GPTM) contains three GPTM blocks. Each GPTM
block provides two 16-bit timers/counters that can be configured to operate independently as timers
or event counters, or configured to operate as one 32-bit timer or one 32-bit Real-Time Clock (RTC).
Timers can also be used to trigger analog-to-digital (ADC) conversions.
When configured in 32-bit mode, a timer can run as a Real-Time Clock (RTC), one-shot timer or
periodic timer. When in 16-bit mode, a timer can run as a one-shot timer or periodic timer, and can
extend its precision by using an 8-bit prescaler. A 16-bit timer can also be configured for event
capture or Pulse Width Modulation (PWM) generation.
Watchdog Timer (see page 370)
A watchdog timer can generate an interrupt or a reset when a time-out value is reached. The
watchdog timer is used to regain control when a system has failed due to a software error or to the
failure of an external device to respond in the expected way.
The Stellaris Watchdog Timer module consists of a 32-bit down counter, a programmable load
register, interrupt generation logic, and a locking register.
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June 18, 2012
Texas Instruments-Production Data