LM3S3748 Datasheet, PDF (592/753 Pages) List of Unclassifed Manufacturers – Microcontroller

Analog Comparators
18.2
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.
VIN- < VIN+, VOUT = 1
VIN- > VIN+, VOUT = 0
As shown in Figure 18-2 on page 592, 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 18-2. Structure of Comparator Unit
-ve input
0
+ve input
1
+ve input (alternate)
CINV
output
IntGen
2
reference input
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 the Comparator Operating Mode tables.
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 the
Comparator Operating Mode tables.
Table 18-1. Comparator 0 Operating Modes
ACCNTL0 Comparator 0
ASRCP VIN- VIN+ Output Interrupt ADC Trigger
00
C0- C0+ C0o/C1+ yes
yes
01
C0- C0+ C0o/C1+ yes
yes
592
April 08, 2008
Preliminary