LM3S3768 Luminary Micro, Inc, LM3S3768 Datasheet - Page 594

• Manufacturer Part Number: LM3S3768
• Description: Lm3s3768 Arm Microcontroller
• Manufacturer: Luminary Micro, Inc

Analog Comparators
18.2
594
Functional Description
Important:
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 594, 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 (alternate)
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:
Table 18-1. Comparator 0 Operating Modes
ACCNTL0
ASRCP
00
01
reference input
+ve input
Comparator 0
VIN-
C0-
C0-
-ve input
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.
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.
VIN+
C0+
C0+
Output
C0o/C1+
C0o/C1+
0
1
2
ACCTL
Interrupt
yes
yes
Preliminary
ADC Trigger
yes
yes
CINV
ACSTAT
TrigGen
IntGen
output
June 02, 2008