© 2004 Microchip Technology Inc. DS70064C-page 17-21
Section 17. 10-bit A/D Converter
10-bit A/D
Converter
17
17.12.2.1 Free Running Sample Conversion Sequence
As shown in Figure 17-7, using the Auto-Convert Conversion Trigger mode (SSRC = 111) in
combination with the Auto-Sample Start mode (ASAM = 1), allows the A/D module to schedule
sample/conversion sequences with no intervention by the user or other device resources. This
“Clocked” mode allows continuous data collection after module initialization. See Example 17-4
for code example.
Figure 17-7: Converting 1 Channel, Auto-Sample Start, T
AD Based Conversion Start
Example 17-4: Converting 1 Channel, Auto-Sample Start,
T
AD Based Conversion Start Code
ADCLK
SAMP
ADCBUF1
TSAMP
TCONV
DONE
= 16 TAD
TSAMP
TCONV
= 16 TAD
ADCBUF0
BSF ADCON1,ASAM
Instruction Execution
ADPCFG = 0xFFFB; // all PORTB = Digital; RB2 = analog
ADCON1 = 0x00E0; // SSRC bit = 111 implies internal
// counter ends sampling and starts
// converting.
ADCHS = 0x0002; // Connect RB2/AN2 as CH0 input ..
// in this example RB2/AN2 is the input
ADCSSL = 0;
ADCON3 = 0x0F00; // Sample time = 15Tad, Tad = internal Tcy/2
ADCON2 = 0x0004; // Interrupt after every 2 samples
ADCON1bits.ADON = 1; // turn ADC ON
while (1) // repeat continuously
{
ADCValue = 0; // clear value
ADC16Ptr = &ADCBUF0; // initialize ADCBUF pointer
IFS0bits.ADIF = 0; // clear ADC interrupt flag
ADCON1bits.ASAM = 1; // auto start sampling
// for 31Tad then go to conversion
while (!IFS0bits.ADIF); // conversion done?
ADCON1bits.ASAM = 0; // yes then stop sample/convert
for (count = 0; count < 2; count++) // average the 2 ADC value
ADCValue = ADCValue + *ADC16Ptr++;
ADCValue = ADCValue >> 1;
} // repeat
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