LM3S1651 Datasheet, PDF (798/1033 Pages) Texas Instruments – ARM and Thumb are registered trademarks and Cortex is a trademark

Analog Comparators
Table 17-3. Internal Reference Voltage and ACREFCTL Field Values (continued)
ACREFCTL Register
EN Bit
Value
RNG Bit Value ^{Output Reference Voltage Based on VREF Field Value}
RNG=0 Total resistance in ladder is 31 R.
VIREF = VDDA × ^RVREF
EN=1
RNG=1
TTohte^VVVVV_VVVV^VV_VVVV^VV_VVVVV^VVVVV_alr^I_I^I_I^I_IIII^IIII_III^II_IIII^IIIIIar^RRR_RRRRRRRRR^RRRRRR_RRRR^RRRRR_enEEE^EEE_EEEEEEs^EEEEEE_EEEE^EEEEEgi^FFF_FFFFFFFFF^FFFFFFFFFFF_FFFFsetaonf⁼⁼⁼⁼⁼₌⁼⁼₌₌₌₌⁼⁼⁼⁼⁼_=======⁼⁼_=cinete^VV_VVVV^VVVVV_VVVVVV^VVVVV000_000000inrn^DDDDDD_D^D_D^D_D^D_D^D_DD^DD_DDDD^..._{......laaDDDDD}^DDDDD_D^DD_DDDD^DDDDD888₈₈₈₁₁₁ld_AAAAA^AAAAA_A^AAAAAAA_AAAArd₄₄₄⁵⁵⁵₅₅₅eef^{×××××}_{××××××}^××_{××××}^{×××××}e_333r r⁺⁺⁺_+++ise^V_VVVV^RRR_RRR^RRRRR(((((_{(×××}n2^VVVVV_Vc⁰⁰⁰₀₀₀^R_RRRR3^VVVVVVVV_VVV^RRRRRRRRRR₂₂₂₂e^RRRRR_RVVV^RRRRRRRR_RRR^..._...R^E_EEEE^TTTTTTTTTTTT₃₃₃₃i^EEEEEEEE_EEE^EEEEE_En_RRR.¹¹¹₁₁₁^F_FFFF^FFFFFFFF_FFF³³³³₃₃^FFFFF_Ft_EEEh⁰⁰⁰₀₀₀¹¹¹¹₁₁i_FFFs⁶⁶⁶₆₆₆⁺⁺⁺⁺⁺₊mo^×××_×××⁸⁸⁸⁸⁸₈de^VVV_VVV⁾⁾⁾⁾⁾₎is^RRR_RRR0^EEE_EEE.8^FFF_FFF5-2.448 V.
VIREF = V0D.D1A4×3 ^V×^R2V^E3R^FEF
VIREF = 0.143 ײV³REF
VIREF = 0.143 × VREF
17.4
The range of internal reference for this mode is 0-2.152 V.
Initialization and Configuration
The following example shows how to configure an analog comparator to read back its output value
from an internal register.
1. Enable the analog comparator clock by writing a value of 0x0010.0000 to the RCGC1 register
in the System Control module (see page 261).
2. Enable the clock to the appropriate GPIO modules via the RCGC2 register (see page 270). To
find out which GPIO ports to enable, refer to Table 21-5 on page 932.
3. In the GPIO module, enable the GPIO port/pin associated with the input signals as GPIO inputs.
To determine which GPIO to configure, see Table 21-4 on page 925.
4. Configure the PMCn fields in the GPIOPCTL register to assign the analog comparator output
signals to the appropriate pins (see page 447 and Table 21-5 on page 932).
798
January 21, 2012
Texas Instruments-Production Data