PIC16F8X_13 Datasheet, PDF (49/128 Pages) Microchip Technology – 18-pin Flash/EEPROM 8-Bit Microcontrollers

PIC16F8X
FIGURE 8-17: INT PIN INTERRUPT TIMING
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
OSC1
CLKOUT 3
4
INT pin
1
INTF flag
5
(INTCON<1>)
GIE bit
(INTCON<7>)
INSTRUCTION FLOW
PC
PC
Instruction
fetched
Inst (PC)
Instruction
executed
Inst (PC-1)
1
PC+1
Inst (PC+1)
Inst (PC)
Interrupt Latency ₂
PC+1
—
Dummy Cycle
0004h
Inst (0004h)
Dummy Cycle
0005h
Inst (0005h)
Inst (0004h)
Note 1: INTF flag is sampled here (every Q1).
2: Interrupt latency = 3-4Tcy where Tcy = instruction cycle time.
Latency is the same whether Inst (PC) is a single cycle or a 2-cycle instruction.
3: CLKOUT is available only in RC oscillator mode.
4: For minimum width of INT pulse, refer to AC specs.
5: INTF is enabled to be set anytime during the Q4-Q1 cycles.
8.9.1 INT INTERRUPT
External interrupt on RB0/INT pin is edge triggered:
either rising if INTEDG bit (OPTION_REG<6>) is set,
or falling, if INTEDG bit is clear. When a valid edge
appears on the RB0/INT pin, the INTF bit
(INTCON<1>) is set. This interrupt can be disabled by
clearing control bit INTE (INTCON<4>). Flag bit INTF
must be cleared in software via the interrupt service
routine before re-enabling this interrupt. The INT
interrupt can wake the processor from SLEEP
(Section 8.12) only if the INTE bit was set prior to going
into SLEEP. The status of the GIE bit decides whether
the processor branches to the interrupt vector
following wake-up.
8.9.2 TMR0 INTERRUPT
An overflow (FFh  00h) in TMR0 will set flag bit T0IF
(INTCON<2>). The interrupt can be enabled/disabled
by setting/clearing enable bit T0IE (INTCON<5>)
(Section 6.0).
8.9.3 PORT RB INTERRUPT
An input change on PORTB<7:4> sets flag bit RBIF
(INTCON<0>). The interrupt can be enabled/disabled
by setting/clearing enable bit RBIE (INTCON<3>)
(Section 5.2).
Note 1: For a change on the I/O pin to be
recognized, the pulse width must be at
least TCY wide.
 1996-2013 Microchip Technology Inc.
DS30430D-page 49