General-Purpose Timers

10 General-Purpose Timers

Programmable timers can be used to count or time external events that drive the Timer input pins. TheStellaris® General-PurposeTimerModule(GPTM)containsfourGPTMblocks(Timer0,Timer1, Timer 2, and Timer 3). Each GPTM block provides two 16-bit timers/counters (referred to as TimerA and TimerB) 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).

In addition, timers can be used to trigger analog-to-digital conversions (ADC). The ADC trigger signals from all of the general-purpose timers are ORed together before reaching the ADC module, so only one timer should be used to trigger ADC events.

The GPT Module is one timing resource available on the Stellaris® microcontrollers. Other timer resources include the System Timer (SysTick) (see “System Timer (SysTick)” on page 46) and the PWM timer in the PWM module (see “PWM Timer” on page 487).

The General-Purpose Timers provide the following features:

■Four General-Purpose Timer Modules (GPTM), each of which provides two 16-bit timers. Each GPTM can be configured to operate independently:

–As a single 32-bit timer

–As one 32-bit Real-Time Clock (RTC) to event capture

–For Pulse Width Modulation (PWM)

–To trigger analog-to-digital conversions

■32-bit Timer modes

–Programmable one-shot timer

–Programmable periodic timer

–Real-Time Clock when using an external 32.768-KHz clock as the input

–Software-controlled event stalling (excluding RTC mode)

–ADC event trigger

■16-bit Timer modes

–General-purposetimerfunctionwithan8-bitprescaler(forone-shotandperiodicmodesonly)

–Programmable one-shot timer

–Programmable periodic timer

–User-enabled stalling when the controller asserts CPU Halt flag during debug

–ADC event trigger

■16-bit Input Capture modes

–Input edge count capture

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LM3S6965 Microcontroller

–Input edge time capture

■16-bit PWM mode

–Simple PWM mode with software-programmable output inversion of the PWM signal

10.1Block Diagram

Note: InFigure10-1onpage219,thespecificCCPpinsavailabledependontheStellaris® device. See Table 10-1 on page 219 for the available CCPs.

Figure 10-1. GPTM Module Block Diagram

Table 10-1. Available CCP Pins

Timer 16-Bit Up/Down CounterEven CCP PinOdd CCP Pin

Preliminary