LM3S9B81 Datasheet, PDF (513/1155 Pages) Texas Instruments – Stellaris® LM3S9B81 Microcontroller

Stellaris® LM3S9B81 Microcontroller
Figure 13-14. 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
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 125). 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 writing a value of 0x0001.0000 to the RCGC0 register (see page 166).
2. Enable the clock to the appropriate GPIO module via the RCGC2 register (see page 183). To
find out which GPIO port to enable, refer to Table 23-5 on page 1043.
3. Set the GPIO AFSEL bits for the ADC input pins (see page 318). To determine which GPIOs to
configure, see Table 23-4 on page 1036.
4. Configure the PMCn fields in the GPIOPCTL register to assign the AINx and VREFA signals to
the appropriate pins (see page 336 and Table 23-5 on page 1043).
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 334) in the associated GPIO block.
June 29, 2010
513
Texas Instruments-Advance Information