T89C51CC02CA-RATIM datasheet(128/159 Pages) ATMEL

128 / 159 page

128

AT/T89C51CC02

4126L–CAN–01/08

The bits SCH0 to SCH2 in ADCON register are used for the analog input channel

selection.

Table 102. Selected Analog input

Voltage Conversion

When the ADCIN is equals to VAREF the ADC converts the signal to 3FFh (full scale). If

the input voltage equals VAGND, the ADC converts it to 000h. Input voltage between

VAREF and VAGND are a straight-line linear conversion. All other voltages will result in

3FFh if greater than VAREF and 000h if less than VAGND.

Note that ADCIN should not exceed VAREF absolute maximum range (See section

“AC-DC”).

Clock Selection

The ADC clock is the same as CPU.

The maximum clock frequency is defined in the DC parmeter for A/D converter. A pres-

caler is featured (ADCCLK) to generate the ADC clock from the oscillator frequency.

if PRS = 0 then F

ADC = Fperiph / 64

if PRS > 0 then F

ADC = Fperiph / 2 x PRS

Figure 54. A/D Converter Clock

ADC Standby Mode

When the ADC is not used, it is possible to set it in standby mode by clearing bit ADEN

in ADCON register. In this mode the power dissipation is reduced.

SCH2

SCH1

SCH0

Selected Analog Input

AN0

AN1

AN2

AN3

AN4

AN5

AN6

AN7

Prescaler ADCLK

A/D

Converter

ADC Clock

CPU

CLOCK

CPU Core Clock Symbol

÷ 2

T89C51CC02CA-RATIM Datasheet(PDF) 128 Page - ATMEL Corporation

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