LM3S5G51 Datasheet, PDF (569/1266 Pages) Texas Instruments – Stellaris® LM3S5G51 Microcontroller

Stellaris^® LM3S5G51 Microcontroller
Figure 12-17. High-Band Operation (CIC=0x3 and/or CTC=0x3)
COMP1
COMP0
Always – 0 0 0 0 1 1 1 0 0 1 1 0 0 0 1 1
Once – 0 0 0 0 1 0 0 0 0 1 0 0 0 0 1 0
Hysteresis Always – 0 0 0 0 1 1 1 1 1 1 1 1 0 0 1 1
Hysteresis Once – 0 0 0 0 1 0 0 0 0 0 0 0 0 0 1 0
12.4
12.4.1
Initialization and Configuration
In order for the ADC module to be used, the PLL must be enabled and programmed to a supported
crystal frequency in the RCC register (see page 215). Using unsupported frequencies can cause
faulty operation in the ADC module.
Module Initialization
Initialization of the ADC module is a simple process with very few steps: enabling the clock to the
ADC, disabling the analog isolation circuit associated with all inputs that are to be used, and
reconfiguring the sample sequencer priorities (if needed).
The initialization sequence for the ADC is as follows:
1. Enable the ADC clock by using the RCGC0 register (see page 259).
2. Enable the clock to the appropriate GPIO modules via the RCGC2 register (see page 276). To
find out which GPIO ports to enable, refer to “Signal Description” on page 552.
3. Set the GPIO AFSEL bits for the ADC input pins (see page 446). To determine which GPIOs to
configure, see Table 23-4 on page 1134.
4. Configure the AINx and VREFA signals to be analog inputs by clearing the corresponding DEN
bit in the GPIO Digital Enable (GPIODEN) register (see page 457).
5. Disable the analog isolation circuit for all ADC input pins that are to be used by writing a 1 to
the appropriate bits of the GPIOAMSEL register (see page 462) in the associated GPIO block.
January 23, 2012
569
Texas Instruments-Production Data