PIC16F720_13 Datasheet, PDF (168/254 Pages) Microchip Technology – 20-Pin Flash Microcontrollers

PIC16(L)F720/721
19.2 Wake-up Using Interrupts
When global interrupts are disabled (GIE cleared) and
any interrupt source has both its interrupt enable bit
and interrupt flag bit set, one of the following will occur:
• If the interrupt occurs before the execution of a
SLEEP instruction, the SLEEP instruction will
complete as a NOP. Therefore, the WDT and WDT
prescaler and postscaler (if enabled) will not be
cleared, the TO bit will not be set and the PD bit
will not be cleared.
• If the interrupt occurs during or after the
execution of a SLEEP instruction, the device will
immediately wake-up from Sleep. The SLEEP
instruction will be completely executed before the
wake-up. Therefore, the WDT and WDT prescaler
and postscaler (if enabled) will be cleared, the TO
bit will be set and the PD bit will be cleared.
Even if the flag bits were checked before executing a
SLEEP instruction, it may be possible for flag bits to
become set before the SLEEP instruction completes. To
determine whether a SLEEP instruction executed, test
the PD bit. If the PD bit is set, the SLEEP instruction
was executed as a NOP.
To ensure that the WDT is cleared, a CLRWDT instruction
should be executed before a SLEEP instruction.
FIGURE 19-1:
WAKE-UP FROM SLEEP THROUGH INTERRUPT
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1
Oscillator
CLKOUT⁽²⁾
INT pin
INTF flag
(INTCON reg.)
GIE bit
(INTCON reg.)
Processor in
Sleep
Instruction Flow
PC
PC
Instruction
Fetched
Inst(PC) = Sleep
Instruction
Executed
Inst(PC - 1)
PC + 1
Inst(PC + 1)
Sleep
PC + 2
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
Interrupt Latency⁽¹⁾
PC + 2
Inst(PC + 2)
Inst(PC + 1)
PC + 2
Dummy Cycle
0004h
Inst(0004h)
Dummy Cycle
0005h
Inst(0005h)
Inst(0004h)
Note 1: GIE = 1 assumed. In this case after wake-up, the processor jumps to 0004h. If GIE = 0, execution will continue in-line.
2: CLKOUT is not available in EC Oscillator mode, but shown here for timing reference.
TABLE 19-1: SUMMARY OF REGISTERS ASSOCIATED WITH POWER-DOWN MODE
Name
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Register on
Page
IOCB
IOCB7 IOCB6 IOCB5 IOCB4
—
—
—
—
56
INTCON
GIE
PEIE TMR0IE INTE RABIE TMR0IF INTF RABIF
38
PIE1
TMR1GIE ADIE
RCIE
TXIE SSPIE CCP1IE TMR2IE TMR1IE
39
PIR1
TMR1GIF ADIF
RCIF
TXIF SSPIF CCP1IF TMR2IF TMR1IF
40
Legend: x = unknown, u = unchanged, – = unimplemented, read as ‘0’. Shaded cells are not used in Power-Down
mode.
DS41430D-page 168
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