PIC16F-ESLASHML datasheet(110/178 Pages) MICROCHIP

110 / 178 page

PIC16F627A/628A/648A

DS40044F-page 108

14.5.1

RB0/INT INTERRUPT

External interrupt on the RB0/INT pin is edge triggered;

either rising if INTEDG bit (OPTION<6>) is set, or

falling, if INTEDG bit is clear. When a valid edge

appears

the

RB0/INT

pin,

the

INTF

bit

(INTCON<1>) is set. This interrupt can be disabled by

clearing the INTE control bit (INTCON<4>). The INTF

bit must be cleared in software in the interrupt service

routine before re-enabling this interrupt. The RB0/INT

interrupt can wake-up the processor from Sleep, if the

INTE bit was set prior to going into Sleep. The status of

the GIE bit decides whether or not the processor

branches to the interrupt vector following wake-up. See

Section 14.8 “Power-Down Mode (Sleep)” for details

on Sleep, and Figure 14-17 for timing of wake-up from

Sleep through RB0/INT interrupt.

14.5.2

TMR0 INTERRUPT

An overflow (FFh

→ 00h) in the TMR0 register will set the

T0IF (INTCON<2>) bit. The interrupt can be enabled/

disabled by setting/clearing T0IE (INTCON<5>) bit. For

operation of the Timer0 module, see Section 6.0

“Timer0 Module”.

14.5.3

PORTB INTERRUPT

An input change on PORTB <7:4> sets the RBIF

(INTCON<0>) bit. The interrupt can be enabled/disabled

by setting/clearing the RBIE (INTCON<3>) bit. For

operation of PORTB (Section 5.2 “PORTB and TRISB

Registers”).

14.5.4

COMPARATOR INTERRUPT

See

Section 10.6

“Comparator

Interrupts”

for

complete description of comparator interrupts.

FIGURE 14-15:

INT PIN INTERRUPT TIMING

Note:

If a change on the I/O pin should occur

when the read operation is being executed

(starts during the Q2 cycle and ends before

the start of the Q3 cycle), then the RBIF

interrupt flag may not get set.

OSC1

CLKOUT

INT pin

INTF flag

(INTCON<1>)

GIE bit

(INTCON<7>)

Instruction Flow

Instruction

Fetched

Instruction

Executed

Interrupt Latency

PC + 1

0004h

0005h

Inst (0004h)

Inst (0005h)

Dummy Cycle

Inst (PC)

Inst (PC + 1)

Inst (PC - 1)

Inst (0004h)

Dummy Cycle

Inst (PC)

—

Note

INTF flag is sampled here (every Q1).

Asynchronous interrupt latency = 3-4 TCY. Synchronous latency = 3 TCY, where TCY = instruction cycle time.

Latency is the same whether Inst (PC) is a single cycle or a two-cycle instruction.

CLKOUT is available in RC and INTOSC oscillator mode.

For minimum width of INT pulse, refer to AC specs.

INTF is enabled to be set anytime during the Q4-Q1 cycles.

(1)

(4)

(5)

(2)

(3)

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