LM3S815_06 Datasheet, PDF (336/412 Pages) List of Unclassifed Manufacturers – Microcontroller

Analog Comparator
15.2
Functional Description
Important: It is recommended that the Digital-Input enable (the GPIODEN bit in the GPIO
module) for the analog input pin be disabled to prevent excessive current draw from
the I/O pads.
The comparator compares the VIN- and VIN+ inputs to produce an output, VOUT.
As shown in Figure 15-2, the input source for VIN- is an external input. In addition to an external
input, input sources for VIN+ can be the +ve input of comparator 0 or an internal reference.
Figure 15-2. Structure of Comparator Unit
-ve input
0
+ve input
1
+ve input (alternate)
CINV
2
reference input
output
IntGen
TrigGen
ACCTL
ACSTAT
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). The operating
modes of the comparators are shown in Table 15-1, Table 15-2 and Table 15-3.
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: Certain register bit values must be set before using the analog comparators. The
proper pad configuration for the comparator input and output pins are described in
Table 8-1 on page 114.
Table 15-1. Comparator 0 Operating Modes
ACCNTL0
Comparator 0
ASRCP
00
01
10
11
VIN-
C0-
C0-
C0-
C0-
VIN+
C0+
C0+
Vref
reserved
Output
C0o
C0o
C0o
C0o
Interrupt
yes
yes
yes
yes
ADCTrigger
yes
yes
yes
yes
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October 8, 2006
Preliminary