LM3S9G97_15 Datasheet, PDF (577/1341 Pages) Texas Instruments – Stellaris LM3S9G97 Microcontroller

Stellaris^® LM3S9G97 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 220). 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 264).
2. Enable the clock to the appropriate GPIO modules via the RCGC2 register (see page 281). To
find out which GPIO ports to enable, refer to “Signal Description” on page 560.
3. Set the GPIO AFSEL bits for the ADC input pins (see page 454). To determine which GPIOs to
configure, see Table 24-4 on page 1202.
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 465).
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 470) in the associated GPIO block.
July 03, 2014
577
Texas Instruments-Production Data