PIC16CE624T-04SS 查看數據表（PDF） - Microchip Technology

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PIC16CE624T-04SS

OTP 8-Bit CMOS MCU with EEPROM Data Memory

Microchip Technology 

The code example in Example 8-1 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 8-1: INITIALIZING

COMPARATOR MODULE

FLAG_REG EQU

0X20

CLRF FLAG_REG ;Init flag register

CLRF PORTA

;Init PORTA

MOVF CMCON,W

;Move comparator contents to W

ANDLW 0xC0

;Mask comparator bits

IORWF FLAG_REG,F ;Store bits in flag register

MOVLW 0x03

;Init comparator mode

MOVWF CMCON

;CM<2:0> = 011

BSF

STATUS,RP0 ;Select Bank1

MOVLW 0x07

;Initialize data direction

MOVWF TRISA

;Set RA<2:0> as inputs

;RA<4:3> as outputs

;TRISA<7:5> always read ‘0’

BCF

STATUS,RP0 ;Select Bank 0

CALL

DELAY 10

;10µs delay

MOVF CMCON,F

;Read CMCON to end change condition

BCF

PIR1,CMIF ;Clear pending interrupts

BSF

STATUS,RP0 ;Select Bank 1

BSF

PIE1,CMIE ;Enable comparator interrupts

BCF

STATUS,RP0 ;Select Bank 0

BSF

INTCON,PEIE ;Enable peripheral interrupts

BSF

INTCON,GIE ;Global interrupt enable

8.2 Comparator Operation

A single comparator is shown in Figure 8-2 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 8-2

represent the uncertainty due to input offsets and

response time.

PIC16CE62X

8.3 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 8-2).

FIGURE 8-2: SINGLE COMPARATOR

VIN+

+

VIN–

–

Output

VVININ––

VVININ++

OOuuttppuut t

8.3.1 EXTERNAL REFERENCE SIGNAL

When external voltage references are used, the

comparator module can be configured to have the com-

parators 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).

8.3.2 INTERNAL REFERENCE SIGNAL

The comparator module also allows the selection of an

internally generated voltage reference for the

comparators. Section 13, 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 8-1). In this mode, the internal

voltage reference is applied to the VIN+ pin of both

comparators.

© 1999 Microchip Technology Inc.

DS40182C-page 43

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