PIC16C717-I/SS View Datasheet(PDF) - Microchip Technology

Part Name

Description

Manufacturer

PIC16C717-I/SS

18/20-Pin, 8-Bit CMOS Microcontrollers with 10/12-Bit A/D

Microchip Technology 

PIC16C717/770/771

FIGURE 11-2: PIC16C717 10-BIT A/D RESULT FORMAT

(ADFM = 0)

(ADFM = 1)

MSB

bit7

bit7

Unused

10-bit A/D Result

MSB

LSB

bit7

bit7

10-bit A/D Result

Unused

LSB

Unused

After the A/D module has been configured as desired,

the selected channel must be acquired before the con-

version is started. The analog input channels must

have their corresponding TRIS and ANSEL bits

selected as an input. To determine acquisition time, see

Section 11.6. After this acquisition time has elapsed,

the A/D conversion can be started. The following steps

should be followed for doing an A/D conversion:

11.2 Configuring the A/D Module

11.2.1 CONFIGURING ANALOG PORT PINS

The ANSEL and TRIS registers control the operation

of the A/D port pins. The port pins that are desired as

analog inputs must have their corresponding TRIS bit

set (input). If the TRIS bit is cleared (output), the digital

output level (VOH or VOL) will be converted. The proper

ANSEL bits must be set (analog input) to disable the

digital input buffer.

The A/D operation is independent of the state of the

TRIS bits and the ANSEL bits.

Note 1: When reading the PORTA or PORTB reg-

ister, all pins configured as analog input

channels will read as ’0’.

2: Analog levels on any pin that is defined as

a digital input, including the ANx pins, may

cause the input buffer to consume current

that is out of the devices specification.

11.2.2 CONFIGURING THE REFERENCE

VOLTAGES

The VCFG bits in the ADCON1 register configure the

A/D module reference inputs. The reference high

input can come from an internal reference (VRH) or

(VRL), an external reference (VREF+), or AVDD. The

low reference input can come from an internal refer-

ence (VRL), an external reference (VREF-), or AVSS. If

an external reference is chosen for the reference high

or reference low inputs, the port pin that multiplexes

the incoming external references is configured as an

analog input, regardless of the values contained in the

A/D port configuration bits (PCFG<3:0>).

DS41120A-page 116

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© 1999 Microchip Technology Inc.

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