LM3S308 Luminary Micro, Inc, LM3S308 Datasheet - Page 368

• Manufacturer Part Number: LM3S308
• Description: Lm3s308 Arm Microcontroller
• Manufacturer: Luminary Micro, Inc

Analog Comparator
15.2.1
368
VIN- < VIN+, VOUT = 1
VIN- > VIN+, VOUT = 0
As shown in Figure 15-2 on page 368, 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 (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 15-1. Comparator 0 Operating Modes
Internal Reference Programming
The structure of the internal reference is shown in Figure 15-3 on page 369. This is controlled by a
single configuration register (ACREFCTL). Table 15-2 on page 369 shows the programming options
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
n/a
n/a
n/a
n/a
ACCTL
Interrupt
yes
yes
yes
yes
Preliminary
ADC Trigger
yes
yes
yes
yes
CINV
ACSTAT
TrigGen
IntGen
output
June 04, 2008