LM3S1439 Luminary Micro, Inc, LM3S1439 Datasheet - Page 411

• Manufacturer Part Number: LM3S1439
• Description: Lm3s1439 Arm Microcontroller
• Manufacturer: Luminary Micro, Inc

16.2.1
July 25, 2008
As shown in Figure 16-2 on page 411, 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 16-2. 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 16-1. Comparator 0 Operating Modes
Internal Reference Programming
The structure of the internal reference is shown in Figure 16-3 on page 412. This is controlled by a
single configuration register (ACREFCTL). Table 16-2 on page 412 shows the programming options
to develop specific internal reference values, to compare an external voltage against a particular
voltage generated internally.
ACCNTL0
ASRCP
00
01
10
11
reference input
+ve input
Comparator 0
VIN-
C0-
C0-
C0-
C0-
-ve input
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+
reserved
C0+
C0+
Vref
Output
0
1
2
C0o
C0o
C0o
C0o
ACCTL
Interrupt
yes
yes
yes
yes
Preliminary
ADC Trigger
yes
yes
yes
yes
CINV
ACSTAT
TrigGen
IntGen
LM3S1439 Microcontroller
output
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