LM3S8938 Datasheet, PDF (484/550 Pages) List of Unclassifed Manufacturers – Microcontroller

Analog Comparators
Figure 18-2. Structure of Comparator Unit
-ve input
0
+ve input
1
+ve input (alternate)
CINV
2
reference input
ACCTL
output
IntGen
TrigGen
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
yes
yes
01
C0- C0+ C0o
yes
yes
10
C0- Vref C0o
yes
yes
11
C0- reserved C0o
yes
yes
Table 18-2. Comparator 1 Operating Modes
ACCNTL1 Comparator 1
ASRCP
00
VIN- VIN+
Output Interrupt ADC Trigger
C1- C1o/C1+^a C1o/C1+ yes
yes
01
C1- C0+ C1o/C1+ yes
yes
10
C1- Vref C1o/C1+ yes
yes
11
C1- reserved C1o/C1+ yes
yes
a. C1o and C1+ signals share a single pin and may only be used as one or the other.
484
June 14, 2007
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