LM3S301 Luminary Micro, Inc, LM3S301 Datasheet - Page 300

• Manufacturer Part Number: LM3S301
• Description: Lm3s301 Arm Microcontroller
• Manufacturer: Luminary Micro, Inc

Analog Comparators
14.3
300
Table 14-3. Internal Reference Voltage and ACREFCTL Field Values (Continued)
Initialization and Configuration
The following example shows how to configure analog comparator to read back its output value
from an internal register.
1.
2.
3.
4.
5.
6.
Change the level of the signal input on C0- to see the OVAL value change.
EN Bit Value
Enable the analog comparator 0 clock by writing a value of 0x00100000 to the RCGC1 register
in the System Control module.
In the GPIO module, enable the GPIO port/pin associated with C0- as a GPIO input.
Configure the internal voltage reference to 1.65 V by writing the ACREFCTL register with the
value 0x0000030C.
Configure comparator 0 to use the internal voltage reference and to not output a value on the
C0O pin by writing the ACCTL0 register with the value of 0x0000040C.
Delay for some time.
Read the comparator output value by reading the ACSTAT0 register’s OVAL value.
EN=1
ACREFCTL Register
RNG Bit Value
RNG=0
RNG=1
Preliminary
Total resistance in ladder is 32 R.
The range of internal reference in this mode is 0.825–2.37 V.
Total resistance in ladder is 24 R.
The range of internal reference for this mode is 0.0–2.0625 V.
Output Reference Voltage Based on VREF Field Value
V
V
REF
REF
V
V
V
V
REF
REF
REF
REF
=
=
=
0.825
AV
=
=
=
AV
AV
AV
0.1375 VREF
DD
DD
+
DD
DD
×
0.103 VREF
(
-----------------------------
×
×
×
VREF
⋅
(
------------------- -
R
--------------- -
R
--------------- -
VREF
VREF
VREF
R
R
32
24
⋅
T
T
+
)
8
)
July 5, 2006