41594B datasheet(152/372 Pages) MICROCHIP

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PIC12LF1840T48A

DS41594B-page 152

Preliminary

 2011-2012 Microchip Technology Inc.

19.3

Comparator Hysteresis

A selectable amount of separation voltage can be

added to the input pins of each comparator to provide a

hysteresis function to the overall operation. Hysteresis

is enabled by setting the C1HYS bit of the CM1CON0

See Section 31.0 “Electrical Specifications” for

more information.

19.4

Timer1 Gate Operation

The output resulting from a comparator operation can

be used as a source for gate control of Timer1. See

Section 21.6 “Timer1 Gate” for more information.

This feature is useful for timing the duration or interval

of an analog event.

It is recommended that the comparator output be syn-

chronized to Timer1. This ensures that Timer1 does not

increment while a change in the comparator is occur-

ring.

19.4.1

COMPARATOR OUTPUT

SYNCHRONIZATION

The output from comparator C1 can be synchronized

with Timer1 by setting the C1SYNC bit of the

CM1CON0 register.

Once enabled, the comparator output is latched on the

falling edge of the Timer1 source clock. If a prescaler is

used with Timer1, the comparator output is latched after

the prescaling function. To prevent a race condition, the

comparator output is latched on the falling edge of the

Timer1 clock source and Timer1 increments on the

rising edge of its clock source. See the Comparator

Block Diagram (Figure 19-2) and the Timer1 Block

Diagram (Figure 21-1) for more information.

19.5

Comparator Interrupt

An interrupt can be generated upon a change in the

output value of the comparator for each comparator, a

rising edge detector and a Falling edge detector are

present.

When either edge detector is triggered and its associ-

ated enable bit is set (C1INTP and/or C1INTN bits of

the CM1CON1 register), the Corresponding Interrupt

Flag bit (C1IF bit of the PIR2 register) will be set.

To enable the interrupt, you must set the following bits:

• C1ON, C1POL and C1SP bits of the CM1CON0

• C1IE bit of the PIE2 register

• C1INTP bit of the CM1CON1 register (for a rising

edge detection)

• C1INTN bit of the CM1CON1 register (for a falling

edge detection)

• PEIE and GIE bits of the INTCON register

The associated interrupt flag bit, C1IF bit of the PIR2

detected while this flag is being cleared, the flag will still

be set at the end of the sequence.

19.6

Comparator Positive Input

Selection

Configuring the C1PCH<1:0> bits of the CM1CON1

analog pin to the non-inverting input of the comparator:

• C1IN+ analog pin

•DAC

• FVR (Fixed Voltage Reference)

•VSS (Ground)

See Section 14.0 “Fixed Voltage Reference (FVR)”

for more information on the Fixed Voltage Reference

module.

See Section 17.0 “Digital-to-Analog Converter

(DAC) Module” for more information on the DAC input

signal.

Any time the comparator is disabled (C1ON = 0), all

comparator inputs are disabled.

Note:

Although a comparator is disabled, an

interrupt can be generated by changing

the output polarity with the C1POL bit of

the CM1CON0 register, or by switching

the comparator on or off with the C1ON bit

of the CM1CON0 register.

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