LM3S1937 Datasheet, PDF (543/673 Pages) Texas Instruments – Stellaris® LM3S1937 Microcontroller

Stellaris^® LM3S1937 Microcontroller
15.3.1
A comparator is configured through two status/control registers (ACCTL and ACSTAT ). The internal
reference is configured through one control register (ACREFCTL). Interrupt status and control is
configured through three registers (ACMIS, ACRIS, and ACINTEN).
Typically, the comparator output is used internally to generate controller interrupts. It may also be
used to drive an external pin or generate an analog-to-digital converter (ADC) trigger.
Important: The ASRCP bits in the ACCTLn register must be set before using the analog
comparators.
Internal Reference Programming
The structure of the internal reference is shown in Figure 15-3 on page 543. This is controlled by a
single configuration register (ACREFCTL). Table 15-3 on page 543 shows the programming options
to develop specific internal reference values, to compare an external voltage against a particular
voltage generated internally.
Figure 15-3. Comparator Internal Reference Structure
AVDD
8R
R
8R
R
R
•••
EN
VREF
RNG
15 14
•••
1
0
Decoder
internal
reference
Table 15-3. Internal Reference Voltage and ACREFCTL Field Values
ACREFCTL Register
EN Bit Value RNG Bit Value
EN=0
RNG=X
Output Reference Voltage Based on VREF Field Value
0 V (GND) for any value of VREF; however, it is recommended that RNG=1 and
VREF=0 for the least noisy ground reference.
June 18, 2012
543
Texas Instruments-Production Data