LM3S6952 Datasheet, PDF (482/626 Pages) Texas Instruments – Stellaris LM3S6952 Microcontroller

Analog Comparators
Figure 17-2. Structure of Comparator Unit
- ve input
+ ve input ⁰
1
+ ve input (alternate)
2
reference input
CINV
ACCTL
output
IntGen
TrigGen
ACSTAT
17.2.1
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 17-3 on page 482. This is controlled by a
single configuration register (ACREFCTL). Table 17-1 on page 482 shows the programming options
to develop specific internal reference values, to compare an external voltage against a particular
voltage generated internally.
Figure 17-3. Comparator Internal Reference Structure
AVDD
8R
R
8R
R
R
•••
EN
VREF
RNG
15 14
•••
1
0
Decoder
internal
reference
Table 17-1. 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.
482
April 05, 2010
Texas Instruments-Production Data