PIC16F753 datasheet(105/230 Pages) MICROCHIP

105 / 230 page

 2013-2015 Microchip Technology Inc.

DS40001709C-page 105

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.

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:

Analog voltages on any pin that is defined

as a digital input may cause the input

buffer 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.

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