LM3S1G21 Datasheet, PDF (619/955 Pages) Texas Instruments – Stellaris® LM3S1G21 Microcontroller

Figure 13-14. High-Band Operation (CIC=0x3)
Stellaris^® LM3S1G21 Microcontroller
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
13.4
13.4.1
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 203). 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 239).
2. Enable the clock to the appropriate GPIO modules via the RCGC2 register (see page 254). To
find out which GPIO ports to enable, refer to “Signal Description” on page 603.
3. Set the GPIO AFSEL bits for the ADC input pins (see page 423). To determine which GPIOs to
configure, see Table 19-4 on page 853.
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 434).
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 439) in the associated GPIO block.
January 22, 2012
619
Texas Instruments-Production Data