LM3S101_0610 Datasheet, PDF (264/300 Pages) List of Unclassifed Manufacturers – Microcontroller

Analog Comparators
13.3
Table 13-3. Internal Reference Voltage and ACREFCTL Field Values (Continued)
ACREFCTL Register
EN Bit Value RNG Bit Value
Output Reference Voltage Based on VREF Field Value
EN=1
RNG=0
Total resistance in ladder is 32 R.
V_REF
=
AV_DD
×
R_{----V----R---E---F-}
R_T
V_REF = AV_DD × ⁽---^V----^R----^E-3---^F-2----+-----8----⁾
RNG=1
V_REF = 0.825 + 0.103 ⋅ VREF
The range of internal reference in this mode is 0.825–2.37 V.
Total resistance in ladder is 24 R.
V_REF
=
AV_DD
×
R_{----V----R---E---F-}
R_T
V_REF = AV_DD × ⁽---^V----^R-2---4^E----^F----⁾
V_REF = 0.1375 ⋅ VREF
The range of internal reference for this mode is 0.0–2.0625 V.
Initialization and Configuration
The following example shows how to configure analog comparator to read back its output value
from an internal register.
1. Enable the analog comparator 0 clock by writing a value of 0x00100000 to the RCGC1 register
in the System Control module.
2. In the GPIO module, enable the GPIO port/pin associated with C0- as a GPIO input.
3. Configure the internal voltage reference to 1.65 V by writing the ACREFCTL register with the
value 0x0000030C.
4. 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.
5. Delay for some time.
6. Read the comparator output value by reading the ACSTAT0 register’s OVAL value.
Change the level of the signal input on C0- to see the OVAL value change.
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October 5, 2006
Preliminary