LM3S1601 Datasheet, PDF (501/587 Pages) Texas Instruments – ARM and Thumb are registered trademarks and Cortex is a trademark

Stellaris^® LM3S1601 Microcontroller
Figure 14-2. Structure of Comparator Unit
-ve input
+ve input ⁰
1
+ve input (alternate)
2
reference input
CINV
output
IntGen
ACCTL
ACSTAT
14.3.1
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.
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 14-3 on page 501. This is controlled by a
single configuration register (ACREFCTL). Table 14-3 on page 501 shows the programming options
to develop specific internal reference values, to compare an external voltage against a particular
voltage generated internally.
Figure 14-3. Comparator Internal Reference Structure
AVDD
8R
R
8R
R
R
•••
EN
VREF
RNG
15 14
•••
1
0
Decoder
internal
reference
Table 14-3. 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 19, 2012
501
Texas Instruments-Production Data