PIC16F87 datasheet(113/230 Pages) MICROCHIP

113 / 230 page

 2002-2013 Microchip Technology Inc.

DS30487D-page 113

PIC16F87/88

12.0

ANALOG-TO-DIGITAL

CONVERTER (A/D) MODULE

The Analog-to-Digital (A/D) converter module has

seven inputs for 18/20 pin devices (PIC16F88 devices

only).

The conversion of an analog input signal results in a

corresponding 10-bit digital number. The A/D module

has a high and low-voltage reference input that is

software selectable to some combination of VDD, VSS,

VREF- (RA2) or VREF+ (RA3).

The A/D converter has a unique feature of being able

to operate while the device is in Sleep mode. To oper-

ate in Sleep, the A/D conversion clock must be derived

from the A/D’s internal RC oscillator.

The A/D module has five registers:

• A/D Result High Register (ADRESH)

• A/D Result Low Register (ADRESL)

• A/D Control Register 0 (ADCON0)

• A/D Control Register 1 (ADCON1)

• Analog Select Register (ANSEL)

The ADCON0 register, shown in

controls the operation of the A/D module. The ANSEL

tions of the port pins. The port pins can be configured

as analog inputs (RA3/RA2 can also be voltage

references) or as digital I/O.

Additional information on using the A/D module can be

found in the “PIC® Mid-Range MCU Family Reference

Manual” (DS33023).

ANSEL:ANALOG SELECT REGISTER(ADDRESS9Bh)PIC16F88DEVICESONLY

U-0

R/W-1

—

ANS6

ANS5

ANS4

ANS3

ANS2

ANS1

ANS0

bit 7

bit 0

bit 7

Unimplemented: Read as ‘0’

bit 6-0

ANS<6:0>: Analog Input Select bits

Bits select input function on corresponding AN<6:0> pins.

= Analog I/O(1,2)

= Digital I/O

Note 1:

Setting a pin to an analog input disables the digital input buffer. The corresponding

TRIS bit should be set to input mode when using pins as analog inputs. Only AN2 is

an analog I/O, all other ANx pins are analog inputs.

See the block diagrams for the analog I/O pins to see how ANSEL interacts with the

CHS bits of the ADCON0 register.

Legend:

R = Readable bit

W = Writable bit

U = Unimplemented bit, read as ‘0’

-n = Value at POR

‘1’ = Bit is set

‘0’ = Bit is cleared

x = Bit is unknown

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