PIC16F753 Datasheet, PDF (114/238 Pages) Microchip Technology – 14/16-Pin, Flash-Based 8-Bit CMOS Microcontrollers

PIC16F753/HV753
12.1 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
• Results formatting
12.1.1 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. See the corresponding port
section for more information.
Note:
Analog voltages on any pin that is defined
as a digital input may cause the input
buffer to conduct excess current.
12.1.2 CHANNEL SELECTION
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 12.2
“ADC Operation” for more information.
12.1.3 ADC VOLTAGE REFERENCE
The ADPREF1 bit of the ADCON1 register provides
control of the positive voltage reference. The positive
voltage reference can be either VDD or an external
voltage source. The negative voltage reference is
always connected to the ground reference.
12.1.4 CONVERSION CLOCK
The source of the conversion clock is software
selectable via the ADCS bits of the ADCON1 register.
There are seven possible clock options:
• FOSC/2
• FOSC/4
• FOSC/8
• FOSC/16
• FOSC/32
• FOSC/64
• FRC (dedicated internal oscillator)
The time to complete one bit conversion is defined as
TAD. One full 10-bit conversion requires 11 TAD periods
as shown in Figure 12-2.
For correct conversion, the appropriate TAD specification
must be met. See A/D conversion requirements in
Section 22.0 “Electrical Specifications” for more
information. Table 12-1 gives examples of appropriate
ADC clock selections.
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.
DS40001709A-page 114
Preliminary
 2013 Microchip Technology Inc.