LM3S1601 Datasheet, PDF (500/587 Pages) Texas Instruments – ARM and Thumb are registered trademarks and Cortex is a trademark

Analog Comparators
14.2
Signal Description
Table 14-1 on page 500 and Table 14-2 on page 500 list the external signals of the Analog Comparators
and describe the function of each. The Analog Comparator output signals are alternate functions
for some GPIO signals and default to be GPIO signals at reset. The column in the table below titled
"Pin Assignment" lists the possible GPIO pin placements for the Analog Comparator signals. The
AFSEL bit in the GPIO Alternate Function Select (GPIOAFSEL) register (page 295) should be set
to choose the Analog Comparator function. The positive and negative input signals 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 272.
Table 14-1. 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
58
O
TTL
Analog comparator 0 output.
C1+
24
I
Analog Analog comparator 1 positive input.
C1-
91
I
Analog Analog comparator 1 negative input.
C1o
2
O
TTL
Analog comparator 1 output.
a. The TTL designation indicates the pin has TTL-compatible voltage levels.
Table 14-2. 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
L9
O
TTL
Analog comparator 0 output.
C1+
M1
I
Analog Analog comparator 1 positive input.
C1-
B7
I
Analog Analog comparator 1 negative input.
C1o
C2
O
TTL
Analog comparator 1 output.
a. The TTL designation indicates the pin has TTL-compatible voltage levels.
14.3 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 14-2 on page 501, 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.
500
June 19, 2012
Texas Instruments-Production Data