LM3S1C26 Datasheet, PDF (453/805 Pages) Texas Instruments – Stellaris® LM3S1C26 Microcontroller

Stellaris^® LM3S1C26 Microcontroller
10.4
10.4.1
■ GPTM Timer B Value (GPTMTBV) register [15:0], see page 487
■ GPTM Timer A Match (GPTMTAMATCHR) register [15:0], see page 478
■ GPTM Timer B Match (GPTMTBMATCHR) register [15:0], see page 479
In the 32-bit modes, the GPTM translates a 32-bit write access to GPTMTAILR into a write access
to both GPTMTAILR and GPTMTBILR. The resulting word ordering for such a write operation is:
GPTMTBILR[15:0]:GPTMTAILR[15:0]
Likewise, a 32-bit read access to GPTMTAR returns the value:
GPTMTBR[15:0]:GPTMTAR[15:0]
A 32-bit read access to GPTMTAV returns the value:
GPTMTBV[15:0]:GPTMTAV[15:0]
Initialization and Configuration
To use a GPTM, the appropriate TIMERn bit must be set in the RCGC1 register (see page 239). If
using any CCP pins, the clock to the appropriate GPIO module must be enabled via the RCGC1
register (see page 239). To find out which GPIO port to enable, refer to Table 18-4 on page 746.
Configure the PMCn fields in the GPIOPCTL register to assign the CCP signals to the appropriate
pins (see page 428 and Table 18-5 on page 750).
This section shows module initialization and configuration examples for each of the supported timer
modes.
One-Shot/Periodic Timer Mode
The GPTM is configured for One-Shot and Periodic modes by the following sequence:
1. Ensure the timer is disabled (the TnEN bit in the GPTMCTL register is cleared) before making
any changes.
2. Write the GPTM Configuration Register (GPTMCFG) with a value of 0x0000.0000.
3. Configure the TnMR field in the GPTM Timer n Mode Register (GPTMTnMR):
a. Write a value of 0x1 for One-Shot mode.
b. Write a value of 0x2 for Periodic mode.
4. Optionally configure the TnSNAPS, TnWOT, TnMTE, and TnCDIR bits in the GPTMTnMR register
to select whether to capture the value of the free-running timer at time-out, use an external
trigger to start counting, configure an additional trigger or interrupt, and count up or down.
5. Load the start value into the GPTM Timer n Interval Load Register (GPTMTnILR).
6. If interrupts are required, set the appropriate bits in the GPTM Interrupt Mask Register
(GPTMIMR).
7. Set the TnEN bit in the GPTMCTL register to enable the timer and start counting.
January 22, 2012
453
Texas Instruments-Production Data