LM3S9B81 Datasheet, PDF (46/1155 Pages) Texas Instruments – Stellaris® LM3S9B81 Microcontroller

Architectural Overview
1.1.1.2
1.1.1.3
■ Memory protection unit (MPU) to provide a privileged mode for protected operating system
functionality
■ Enhanced system debug with extensive breakpoint and trace capabilities
■ Serial Wire Debug and Serial Wire Trace reduce the number of pins required for debugging and
tracing
■ Migration from the ARM7™ processor family for better performance and power efficiency
■ Optimized for single-cycle Flash memory usage
■ Ultra-low power consumption with integrated sleep modes
■ 80-MHz operation
■ 1.25 DMIPS/MHz
“ARM Cortex-M3 Processor Core” on page 66 provides an overview of the ARM core; the core is
detailed in the ARM® Cortex™-M3 Technical Reference Manual.
System Timer (SysTick) (see page 76)
ARM Cortex-M3 includes an integrated system timer, SysTick. SysTick provides a simple, 24-bit,
clear-on-write, decrementing, wrap-on-zero counter with a flexible control mechanism. The counter
can be used in several different ways, for example:
■ An RTOS tick timer that fires at a programmable rate (for example, 100 Hz) and invokes a SysTick
routine
■ A high-speed alarm timer using the system clock
■ A variable rate alarm or signal timer—the duration is range-dependent on the reference clock
used and the dynamic range of the counter
■ A simple counter used to measure time to completion and time used
■ An internal clock-source control based on missing/meeting durations. The COUNTFLAG field in
the SysTick Control and Status register can be used to determine if an action completed within
a set duration, as part of a dynamic clock management control loop
Nested Vectored Interrupt Controller (NVIC) (see page 82)
The LM3S9B81 controller includes the ARM Nested Vectored Interrupt Controller (NVIC). The NVIC
and Cortex-M3 prioritize and handle all exceptions in Handler Mode. The processor state is
automatically stored to the stack on an exception and automatically restored from the stack at the
end of the Interrupt Service Routine (ISR). The interrupt vector is fetched in parallel to the state
saving, enabling efficient interrupt entry. The processor supports tail-chaining, meaning that
back-to-back interrupts can be performed without the overhead of state saving and restoration.
Software can set eight priority levels on 7 exceptions (system handlers) and 47 interrupts.
■ Deterministic, fast interrupt processing: always 12 cycles, or just 6 cycles with tail-chaining
■ External non-maskable interrupt signal (NMI) available for immediate execution of NMI handler
for safety critical applications
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June 29, 2010
Texas Instruments-Advance Information