PIC16C62B-04 Datasheet, PDF(41/128 Page) Microchip Technology – EPROM-Based 8-Bit CMOS Microcontrollers

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PIC16C62B-04 Datasheet, PDF (41/128 Pages) Microchip Technology – EPROM-Based 8-Bit CMOS Microcontrollers

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The code example in Example 7-1 depicts the steps

required to configure the comparator module. RA3 and

RA4 are configured as digital output. RA0 and RA1 are

configured as the V- inputs and RA2 as the V+ input to

both comparators.

EXAMPLE 7-1:

INITIALIZING

COMPARATOR MODULE

MOVLW

MOVWF

CLRF

BSF

MOVLW

MOVWF

BCF

CALL

MOVF

BCF

BSF

BCF

BSF

0x03

;Init comparator mode

CMCON

;CM<2:0> = 011

PORTA

;Init PORTA

STATUS,RP0 ;Select Bank1

0x07

;Initialize data direction

TRISA

;Set RA<2:0> as inputs

;RA<4:3> as outputs

;TRISA<7:5> always read â0â

STATUS,RP0 ;Select Bank 0

DELAY 10

;10Âµs delay

CMCON,F

;Read CMCONtoend changecondition

PIR1,CMIF ;Clear pending interrupts

STATUS,RP0 ;Select Bank 1

PIE1,CMIE ;Enable comparator interrupts

STATUS,RP0 ;Select Bank 0

INTCON,PEIE ;Enable peripheral interrupts

INTCON,GIE ;Global interrupt enable

7.2 Comparator Operation

A single comparator is shown in Figure 7-2 along with

the relationship between the analog input levels and

the digital output. When the analog input at VIN+ is less

than the analog input VIN-, the output of the comparator

is a digital low level. When the analog input at VIN+ is

greater than the analog input VIN-, the output of the

comparator is a digital high level. The shaded areas of

the output of the comparator in Figure 7-2 represent

the uncertainty due to input offsets and response time.

PIC16C62X

7.3 Comparator Reference

An external or internal reference signal may be used

depending on the comparator Operating mode. The

analog signal that is present at VIN- is compared to the

signal at VIN+, and the digital output of the comparator

is adjusted accordingly (Figure 7-2).

FIGURE 7-2:

SINGLE COMPARATOR

VIN+

VIN-

Output

VVININ-â

VVININ++

Ouuttppuut t

7.3.1

EXTERNAL REFERENCE SIGNAL

When external voltage references are used, the

comparator module can be configured to have the

comparators operate from the same or different

reference sources. However, threshold detector

applications may require the same reference. The

reference signal must be between VSS and VDD, and

can be applied to either pin of the comparator(s).

7.3.2

INTERNAL REFERENCE SIGNAL

The comparator module also allows the selection of an

internally generated voltage reference for the

comparators. Section 10, Instruction Sets, contains a

detailed description of the Voltage Reference Module

that provides this signal. The internal reference signal

is used when the comparators are in mode

CM<2:0>=010 (Figure 7-1). In this mode, the internal

voltage reference is applied to the VIN+ pin of both

comparators.

DS30235J-page 39

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