LM3S2730 Luminary Micro, Inc, LM3S2730 Datasheet - Page 353

• Manufacturer Part Number: LM3S2730
• Description: Lm3s2730 Arm Microcontroller
• Manufacturer: Luminary Micro, Inc

14.2
July 25, 2008
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 14-2 on page 353, 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 14-2. 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.
Important:
Table 14-1. 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
0
1
2
C0o
C0o
ACCTL
Interrupt
yes
yes
Preliminary
CINV
ACSTAT
IntGen
LM3S2730 Microcontroller
output
353