LM3S1937 Datasheet, PDF (542/673 Pages) Texas Instruments – Stellaris® LM3S1937 Microcontroller

Analog Comparator
bit in the GPIO Alternate Function Select (GPIOAFSEL) register (page 302) should be set to choose
the Analog Comparator function. The positive and negative input signal are configured by clearing
the DEN bit in the GPIO Digital Enable (GPIODEN) register. For more information on configuring
GPIOs, see “General-Purpose Input/Outputs (GPIOs)” on page 278.
Table 15-1. Analog Comparators Signals (100LQFP)
Pin Name
Pin Number Pin Type Buffer Type^a Description
C0+
90
I
Analog Analog comparator 0 positive input.
C0-
92
I
Analog Analog comparator 0 negative input.
C0o
91
O
TTL
Analog comparator 0 output.
a. The TTL designation indicates the pin has TTL-compatible voltage levels.
Table 15-2. Analog Comparators Signals (108BGA)
Pin Name
Pin Number Pin Type Buffer Type^a Description
C0+
A7
I
Analog Analog comparator 0 positive input.
C0-
A6
I
Analog Analog comparator 0 negative input.
C0o
B7
O
TTL
Analog comparator 0 output.
a. The TTL designation indicates the pin has TTL-compatible voltage levels.
15.3 Functional Description
Important: 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.
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 15-2 on page 542, 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
+ ve input ⁰
1
+ ve input (alternate)
2
reference input
CINV
output
IntGen
TrigGen
ACCTL
ACSTAT
542
June 18, 2012
Texas Instruments-Production Data