Rainbow-electronics ATmega128L Uživatelský manuál stáhnout pdf (Strana 233)

233

ATmega128(L)

2467B–09/01

Example:

ADMUX = 0xED (ADC3 - ADC2, 10x gain, 2.56V reference, left adjusted result)

Voltage on ADC3 is 300 mV, voltage on ADC2 is 500 mV.

ADCR = 512 * 10 * (300 - 500) / 2560 = -400 = 0x270

ADCL will thus read 0x00, and ADCH will read 0x9C. Writing zero to ADLAR right

adjusts the result: ADCL = 0x70, ADCH = 0x02.

ADC Multiplexer Selection

• Bit 7:6 - REFS1:0: Reference Selection Bits

These bits select the voltage reference for the ADC, as shown in

Table 96. If these bits

are changed during a conversion, the change will not go in effect until this conversion is

complete (ADIF in ADCSRA is set). The internal voltage reference options may not be

used if an external reference voltage is being applied to the AREF pin.

•

Bit 5 - ADLAR: ADC Left Adjust Result

The ADLAR bit affects the presentation of the ADC conversion result in the ADC data

adjusted. Changing the ADLAR bit will affect the ADC data register immediately,

Table 95. Correlation Between Input Voltage and Output Codes

ADCn

Read code Corresponding decimal value

ADCm

+ V

REF

/ GAIN 0x1FF 511

ADCm

+ 0.999 V

REF

/ GAIN 0x1FF 511

ADCm

+ 0.998 V

REF

/ GAIN 0x1FE 510

... ... ...

ADCm

+ 0.001 V

REF

/ GAIN 0x001 1

ADCm

0x000 0

ADCm

- 0.001 V

REF

/ GAIN 0x3FF -1

... ... ...

ADCm

- 0.999 V

REF

/ GAIN 0x201 -511

ADCm

- V

REF

/ GAIN 0x200 -512

Bit 76543210

REFS1 REFS0 ADLAR MUX4 MUX3 MUX2 MUX1 MUX0 ADMUX

Read/Write R/W R/W R/W R/W R/W R/W R/W R/W

Initial value00000000

Table 96. Voltage Reference Selections for ADC

REFS1 REFS0 Voltage Reference Selection

0 0 AREF, Internal Vref turned off

0 1 AVCC with external capacitor at AREF pin

10Reserved

1 1 Internal 2.56V Voltage Reference with external capacitor at AREF pin

1 2 ... 228 229 230 231 232 233 234 235 236 237 238 ... 330 331

Komentáře k této Příručce

Žádné komentáře

Rainbow-electronics ATmega128L Uživatelský manuál Strana 233

Komentáře k této Příručce

Související produkty a manuály pro Senzory Rainbow-electronics ATmega128L