LM3S2793 Datasheet, PDF (558/1194 Pages) Texas Instruments – Stellaris® LM3S2793 Microcontroller

General-Purpose Timers
11.3.4
11.4
11.4.1
No other special steps are needed to enable Timers for μDMA operation. Refer to “Micro Direct
Memory Access (μDMA)” on page 359 for more details about programming the μDMA controller.
Accessing Concatenated Register Values
The GPTM is placed into concatenated mode by writing a 0x0 or a 0x1 to the GPTMCFG bit field in
the GPTM Configuration (GPTMCFG) register. In both configurations, certain registers are
concatenated to form pseudo 32-bit registers. These registers include:
■ GPTM Timer A Interval Load (GPTMTAILR) register [15:0], see page 581
■ GPTM Timer B Interval Load (GPTMTBILR) register [15:0], see page 582
■ GPTM Timer A (GPTMTAR) register [15:0], see page 589
■ GPTM Timer B (GPTMTBR) register [15:0], see page 590
■ GPTM Timer A Value (GPTMTAV) register [15:0], see page 591
■ GPTM Timer B Value (GPTMTBV) register [15:0], see page 592
■ GPTM Timer A Match (GPTMTAMATCHR) register [15:0], see page 583
■ GPTM Timer B Match (GPTMTBMATCHR) register [15:0], see page 584
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 270). If
using any CCP pins, the clock to the appropriate GPIO module must be enabled via the RCGC1
register (see page 270). To find out which GPIO port to enable, refer to Table 23-4 on page 1070.
Configure the PMCn fields in the GPIOPCTL register to assign the CCP signals to the appropriate
pins (see page 459 and Table 23-5 on page 1078).
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.
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January 20, 2012
Texas Instruments-Production Data