LM3S2276 Datasheet, PDF (402/785 Pages) Texas Instruments – Stellaris® LM3S2276 Microcontroller

General-Purpose Timers
Register (GPTMTnMATCHR). Software has the capability of inverting the output PWM signal by
setting the TnPWML bit in the GPTMCTL register.
Figure 10-4 on page 402 shows how to generate an output PWM with a 1-ms period and a 66% duty
cycle assuming a 50-MHz input clock and TnPWML =0 (duty cycle would be 33% for the TnPWML
=1 configuration). For this example, the start value is GPTMTnIRL=0xC350 and the match value is
GPTMTnMATCHR=0x411A.
Figure 10-4. 16-Bit PWM Mode Example
Count
GPTMTnR=GPTMnMR
0xC350
GPTMTnR=GPTMnMR
0x411A
TnEN set
Output
Signal
TnPWML = 0
TnPWML = 1
Time
10.4
10.4.1
Initialization and Configuration
To use the general-purpose timers, the peripheral clock must be enabled by setting the TIMER0,
TIMER1, and TIMER2 bits in the RCGC1 register.
This section shows module initialization and configuration examples for each of the supported timer
modes.
32-Bit One-Shot/Periodic Timer Mode
The GPTM is configured for 32-bit One-Shot and Periodic modes by the following sequence:
1. Ensure the timer is disabled (the TAEN bit in the GPTMCTL register is cleared) before making
any changes.
2. Write the GPTM Configuration Register (GPTMCFG) with a value of 0x0.
3. Set the TAMR field in the GPTM TimerA Mode Register (GPTMTAMR):
a. Write a value of 0x1 for One-Shot mode.
b. Write a value of 0x2 for Periodic mode.
402
November 17, 2011
Texas Instruments-Production Data