AT83C5111 datasheet(56/86 Pages) ATMEL

56 / 86 page

AT8xC5111

4190A–8051–11/02

ADC Operation

Before starting a conversion, the A/D converter must be enabled, by setting the ADEN

bit, for at least T

setup (four microseconds).

A start of single A/D conversion is triggered by setting bit ADSST (ADCON.3).

From the ADSST set, the first full CONV_CK period will be the sampling period for the

ADC; during this period, the switch is closed and the capacitor is being charged. At the

end of the first period, the switch opens and the capacitor is no longer being charged.

During the next 10 CONV_CK periods, the sample and hold will be in hold mode during

the conversion. The busy flag ADSST(ADCON.3) remains set as long as an A/D conver-

sion is running. After completion of the A/D conversion, it is cleared by hardware. When

a conversion is running, this flag can be read only, a write has no effect.

The end-of-conversion flag ADEOC (ADCON.4) is set when the value of conversion is

available in ADDH and ADDL, it is cleared by software. If the bit EADC (IE1.1) is set, an

interrupt occur when flag ADEOC is set (see Figure 28). Clear this flag for re-arming the

interrupt.

From this point, if you keep starting a new conversion by resetting ADSST without

changing ADEN, it is not necessary to wait T

setup.

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

selection.

Before starting normal power reduction modes the ADC conversion has to be com-

pleted.

Table 1. Selected Analog Input

Voltage Conversion

When the ADCIN is equal 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.

SCH2

SCH1

SCH0

Selected Analog Input

AN0

AN1

AN2

AN3

AN4

AN5

AN6

AN7

AT83C5111 数据表(PDF) 56 Page - ATMEL Corporation

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