Datasheet

 2012 Microchip Technology Inc. DS30575A-page 463
PIC18F97J94 FAMILY
22.5.2 CLOCKED CONVERSION TRIGGER
When ADRC = 1, the conversion trigger is under A/D
clock control. The SAMCx bits (ADCON3H<4:0>)
select the number of TAD clock cycles between the
start of sampling and the start of conversion. After the
start of sampling, the module will count a number of
TAD clocks specified by the SAMCx bits. The SAMCx
bits must always be programmed for at least one clock
cycle to ensure sampling requirements are met.
EQUATION 22-2: CLOCKED CONVERSION
TRIGGER TIME
Figure 22-6 shows how to use the clocked conversion
trigger with the sampling started by the user software.
FIGURE 22-6: CONVERTING ONE CHANNEL, MANUAL SAMPLE START, TAD-BASED
CONVERSION START
EXAMPLE 22-2: CONVERTING ONE CHANNEL, MANUAL SAMPLE START, T
AD-BASED
CONVERSION START CODE
TSMP = SAMC<4:0> * TAD
A/D CLK
SAMP
ADC1BUF0
TSAMP TCONV
BSF AD1CON1, SAMPInstruction Execution
DONE
int ADCValue;
ANSB = 0x1000; // all PORTB = Digital; RB12 = analog
AD1CON1 = 0x00E0; // SSRC<2:0> = 111 implies internal counter ends sampling
// and starts converting.
AD1CHS = 0x000C; // Connect AN12 as S/H input.
// in this example AN12 is the input
AD1CSSL = 0;
AD1CON3 = 0x1F02; // Sample time = 31Tad, Tad = 3Tcy
AD1CON2 = 0;
AD1CON1bits.ADON = 1; // turn ADC ON
while (1) // repeat continuously
{
AD1CON1bits.SAMP = 1; // start sampling, then after 31Tad go to conversion
while (!AD1CON1bits.DONE){}; // conversion done?
ADCValue = ADC1BUF0; // yes then get ADC value
} // repeat