LM3S5956-IQR80-C1 Datasheet, PDF (936/1144 Pages) Texas Instruments – Stellaris® LM3S5956 Microcontroller

Analog Comparators
NRND: Not recommended for new designs.
18.2
Signal Description
The following table lists the external signals of the Analog Comparators and describes 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 Mux/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 431) should be set to choose the
Analog Comparator function. The number in parentheses is the encoding that must be programmed
into the PMCn field in the GPIO Port Control (GPIOPCTL) register (page 448) to assign the Analog
Comparator signal to the specified GPIO port pin. 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 411.
Table 18-1. Analog Comparators Signals (64LQFP)
Pin Name
Pin Number Pin Mux / Pin Pin Type Buffer Type^a Description
Assignment
C0+
56
PB6
I
Analog Analog comparator 0 positive input.
C0-
58
PB4
I
Analog Analog comparator 0 negative input.
C0o
14
PC5 (3)
O
TTL
Analog comparator 0 output.
56
PB6 (3)
57
PB5 (1)
C1+
16
PC7
I
Analog Analog comparator 1 positive input.
C1-
57
PB5
I
Analog Analog comparator 1 negative input.
C1o
14
PC5 (2)
O
TTL
Analog comparator 1 output.
16
PC7 (7)
a. The TTL designation indicates the pin has TTL-compatible voltage levels.
18.3
Functional Description
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 18-2 on page 937, the input source for VIN- is an external input, Cn-. In addition
to an external input, Cn+, input sources for VIN+ can be the C0+ or an internal reference, V_IREF.
936
October 06, 2012
Texas Instruments-Production Data