Datasheet

PIC12(L)F1501
DS41615A-page 114 Preliminary  2011 Microchip Technology Inc.
15.1 ADC Configuration
When configuring and using the ADC the following
functions must be considered:
• Port configuration
• Channel selection
• ADC voltage reference selection
• ADC conversion clock source
• Interrupt control
• Result formatting
15.1.1 PORT CONFIGURATION
The ADC can be used to convert both analog and
digital signals. When converting analog signals, the I/O
pin should be configured for analog by setting the
associated TRIS and ANSEL bits. Refer to
Section 11.0 “I/O Ports” for more information.
15.1.2 CHANNEL SELECTION
There are 7 channel selections available:
• AN<3:0> pins
• Temperature Indicator
•DAC
• FVR (Fixed Voltage Reference) Output
Refer to
Section 13.0 “Fixed Voltage Reference (FVR)”
and Section 14.0 “Temperature Indicator Module” for
more information on these channel selections.
The CHS bits of the ADCON0 register determine which
channel is connected to the sample and hold circuit.
When changing channels, a delay is required before
starting the next conversion. Refer to
Section 15.2
“ADC Operation”
for more information.
15.1.3 ADC VOLTAGE REFERENCE
The ADPREF bits of the ADCON1 register provides
control of the positive voltage reference. The positive
voltage reference can be:
•V
REF+ pin
•V
DD
See Section 13.0 “Fixed Voltage Reference (FVR)”
for more details on the Fixed Voltage Reference.
15.1.4 CONVERSION CLOCK
The source of the conversion clock is software select-
able via the ADCS bits of the ADCON1 register. There
are seven possible clock options:
•F
OSC/2
•F
OSC/4
•F
OSC/8
•F
OSC/16
•F
OSC/32
•F
OSC/64
•F
RC (dedicated internal oscillator)
The time to complete one bit conversion is defined as
T
AD. One full 10-bit conversion requires 11.5 TAD peri-
ods as shown in Figure 15-2.
For correct conversion, the appropriate T
AD specifica-
tion must be met. Refer to the A/D conversion require-
ments in
Section 27.0 “Electrical Specifications” for
more information. Table 15-1 gives examples of appro-
priate ADC clock selections.
Note: Analog voltages on any pin that is defined
as a digital input may cause the input buf-
fer to conduct excess current.
Note: Unless using the FRC, any changes in the
system clock frequency will change the
ADC clock frequency, which may
adversely affect the ADC result.