Datasheet

 2012 Microchip Technology Inc. DS30575A-page 465
PIC18F97J94 FAMILY
22.5.3.4 Sample Time Considerations For
Automatic Sampling/conversion
Sequences
Different sample/conversion sequences provide differ-
ent available sampling times for the S/H channel to
acquire the analog signal. The user must ensure the
sampling time satisfies the sampling requirements, as
outlined in Section 22.9 “A/D Sampling Require-
ments”.
Assuming that the module is set for automatic sam-
pling, and an external trigger pulse is used as the con-
version trigger, the sampling interval is a portion of the
trigger pulse interval. The sampling time is the trigger
pulse period, less the time required to complete the
conversion.
EQUATION 22-3: CALCULATING AVAILABLE SAMPLING TIME FOR SEQUENTIAL SAMPLING
FIGURE 22-8: MANUAL SAMPLE START, CONVERSION TRIGGER-BASED CONVERSION
START
FIGURE 22-9: AUTO-SAMPLE START, CONVERSION TRIGGER-BASED CONVERSION START
TSMP = Trigger Pulse Interval (TSEQ) – Conversion Time (TCONV) = TSEQ – TCONV
Conversion Trigger
A/D CLK
SAMP
ADC1BUF0
TSAMP TCONV
BSF AD1CON1, SAMP
Instruction Execution
Conversion Trigger
A/D CLK
SAMP
ADC1BUF0
TSAMP TCONV
BSF AD1CON1, ASAM
TCONVTSAMP
ADC1BUF1
DONE
Reset by
Software
Instruction Execution