LM3S1D21 Datasheet, PDF (46/956 Pages) Texas Instruments – Stellaris® LM3S1D21 Microcontroller

Architectural Overview
1.3.5.3
– 3.3-V supply brown-out detection and reporting via interrupt or reset
■ Multiple clock sources for microcontroller system clock
– Precision Oscillator (PIOSC): On-chip resource providing a 16 MHz ±1% frequency at room
temperature
• 16 MHz ±3% across temperature
• Can be recalibrated with 7-bit trim resolution
• Software power down control for low power modes
– Main Oscillator (MOSC): A frequency-accurate clock source by one of two means: an external
single-ended clock source is connected to the OSC0 input pin, or an external crystal is
connected across the OSC0 input and OSC1 output pins.
• External crystal used with or without on-chip PLL: select supported frequencies from 1
MHz to 16.384 MHz.
• External oscillator: from DC to maximum device speed
– Internal 30-kHz Oscillator: on chip resource providing a 30 kHz ± 50% frequency, used during
power-saving modes
– 32.768-kHz external oscillator for the Hibernation Module: eliminates need for additional
crystal for main clock source
■ Flexible reset sources
– Power-on reset (POR)
– Reset pin assertion
– Brown-out reset (BOR) detector alerts to system power drops
– Software reset
– Watchdog timer reset
– MOSC failure
Programmable Timers (see page 531)
Programmable timers can be used to count or time external events that drive the Timer input pins.
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.
The General-Purpose Timer Module (GPTM) contains four GPTM blocks with the following functional
options:
■ Operating modes:
– 16- or 32-bit programmable one-shot timer
– 16- or 32-bit programmable periodic timer
– 16-bit general-purpose timer with an 8-bit prescaler
– 32-bit Real-Time Clock (RTC) when using an external 32.768-KHz clock as the input
46
January 22, 2012
Texas Instruments-Production Data