PFS123 datasheet(65/104 Pages) PADAUK

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PFS123

8bit MTP MCU with 12-bit R-Type ADC

Page 65 of 104

PDK-DS-PFS123-EN_V000-Aug. 26, 2020

5.15.4 Configure the analog pins

There are 14 analog signals can be selected for AD conversion, 13 analog input signals come from external

pins and one is from internal band-gap reference voltage 1.2V. For those external pins defined as analog

input, to avoid leakage current from the digital circuit of the shared IO ports, please always remember to

disable the digital input function (set the corresponding bit of padier, pbdier or pcdier register to be 0).

Due to the measurement signals of ADC are very small; user should avoid the measured signal to be

interfered during the measurement period. Thus, the selected pin should (1) be set to input mode (2) turn

off weak pull-high and pull-low resistor (3) set the corresponding pin to analog input by port A/B/C digital

input disable register (padier / pbdier / pcdier).

5.15.5 Using the ADC

The following example shows how to use ADC with PB0~PB3.

First, defining the selected pins:

PBC

0B_XXXX_0000;

PB0 ~ PB3 as Input

PBPH

0B_XXXX_0000;

PB0 ~ PB3 without pull-high resistor

PBPL

0B_XXXX_00XX;

PB2 ~ PB3 without pull-low resistor

PBDIER

0B_XXXX_0000;

PB0 ~ PB3 digital input is disabled

Next, setting ADCC register, example as below:

ADCC

Enable, PB3;

set PB3 as ADC input

ADCC

Enable, PB2;

set PB2 as ADC input

ADCC

Enable, PB0;

set PB0 as ADC input

Next, setting ADCM register, example as below:

ADCM /16;

recommend /16 @System Clock=8MHz

ADCM /8;

recommend /8 @System Clock=4MHz

Next, delay 400us, example as below:

.Delay 8*400;

System Clock=8MHz

.Delay 4*400;

System Clock=4MHz

Then, start the ADC conversion:

AD_START =

// start ADC conversion

while(!AD_DONE) NULL;

// wait ADC conversion result

Finally, it can read ADC result when AD_DONE is high:

WORD

Data;

two bytes result: ADCRH and ADCRL

Data$1

ADCRH;

Data$0

ADCRL;

Data

Data >> 4;

The ADC can be disabled by using the following method:

ADCC

Disable;

ADCC

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