AT83SND1CXXX-ROTIL datasheet(173/212 Pages) ATMEL

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173

4109J–8051–10/06

AT8xC51SND1C

20. Analog to Digital Converter

The AT8xC51SND1C implement a 2-channel 10-bit (8 true bits) analog to digital converter

(ADC). First channel of this ADC can be used for battery monitoring while the second one can

be used for voice sampling at 8 kHz.

20.1

Description

The A/D converter interfaces with the C51 core through four special function registers: ADCON,

the ADC control register (see Table 137); ADDH and ADDL, the ADC data registers (see Table

139 and Table 140); and ADCLK, the ADC clock register (see Table 138).

As shown in Figure 20-1, the ADC is composed of a 10-bit cascaded potentiometric digital to

analog converter, connected to the negative input of a comparator. The output voltage of this

DAC is compared to the analog voltage stored in the Sample and Hold and coming from AIN0 or

AIN1 input depending on the channel selected (see Table 136). The 10-bit ADDAT converted

value (see formula in Figure 20-1) is delivered in ADDH and ADDL registers, ADDH is giving the

8 most significant bits while ADDL is giving the 2 least significant bits. ADDAT

Figure 20-1. ADC Structure

Figure 20-2 shows the timing diagram of a complete conversion. For simplicity, the figure depicts

the waveforms in idealized form and do not provide precise timing information. For ADC charac-

teristics and timing parameters refer to the section “AC Characteristics”.

AIN1

AIN0

ADCS

ADCON.0

AVSS

Sample and Hold

ADDH

AREFP

R/2R DAC

ADC

CLOCK

AREFN

ADEN

ADCON.5

ADSST

ADCON.3

ADEOC

ADCON.4

ADC

Interrupt

Request

EADC

IEN1.3

CONTROL

ADDL

SAR

ADDAT

1023 V

⋅

REF

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