PIC16C64X datasheet(49/136 Pages) MICROCHIP

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Preliminary

DS30559A-page 49

PIC16C64X & PIC16C66X

The code example in Example 7-1 depicts the steps

required to conﬁgure the comparator module. RA3 and

RA4 are conﬁgured as digital outputs. RA0 and RA1

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

to both comparators.

EXAMPLE 7-1:

INITIALIZING THE

COMPARATOR MODULE

FLAG_REG

EQU 0x20

CLRF

FLAG_REG

;Init Flag Register

CLRF

PORTA

;Init PORTA

ANDLW

0xC0

;Mask Comp bits

IORWF

FLAG_REG,F

;Bits to Flag_Reg

MOVLW

0x03

;Init Comp Mode

MOVWF

CMCON

;CM2:CM0 = 011

BSF

STATUS,RP0

;Select Bank 1

MOVLW

0x07

;Init Data direction

MOVWF

TRISA

;RA<2:0> to inputs

;RA<4:3> to outputs

;TRISA<7:5> read '0'

BCF

STATUS,RP0

;Select Bank 0

CALL

DELAY_10

µs

;10

µs delay

MOVF

CMCON,F

;Read CMCON to end

;change condition

BCF

PIR1,CMIF

;Clear Pending Ints

BSF

STATUS,RP0

;Select Bank 1

BSF

PIE1,CMIE

;Enable Comp Ints

BCF

STATUS,RP0

;Select Bank 0

BSF

INTCON,PEIE

;Enable Periph Ints

BSF

INTCON,GIE

;Global Int enable

7.2

Comparator Operation

A single comparator is shown in Figure 7-3 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 7-3 represents

the uncertainty due to input offsets and response time.

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 7-3).

FIGURE 7-3:

SINGLE COMPARATOR

7.3.1

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).

7.3.2

INTERNAL REFERENCE SIGNAL

The comparator module also allows the selection of an

internally

generated

voltage

reference

for

the

comparators. Section 8.0, contains a detailed descrip-

tion of the Voltage Reference Module that provides this

signal. The internal reference signal is used when the

comparators

are

mode

CM2:CM0 = 010

(Figure 7-2). In this mode, the internal voltage refer-

ence is applied to the VIN+ pin of both comparators.

VIN-

VIN+

Output

VIN-

VIN+

Output

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