PIC12F1840 MICROCHIP [Microchip Technology], PIC12F1840 Datasheet - Page 79

• Manufacturer Part Number: PIC12F1840
• Description: 8-Pin Flash Microcontrollers with nanoWatt XLP Technology
• Manufacturer: MICROCHIP [Microchip Technology]

8.1
Interrupts are disabled upon any device Reset. They
are enabled by setting the following bits:
• GIE bit of the INTCON register
• Interrupt Enable bit(s) for the specific interrupt
• PEIE bit of the INTCON register (if the Interrupt
The INTCON, PIR1 and PIR2 registers record individual
interrupts via interrupt flag bits. Interrupt flag bits will be
set, regardless of the status of the GIE, PEIE and
individual interrupt enable bits.
The following events happen when an interrupt event
occurs while the GIE bit is set:
• Current prefetched instruction is flushed
• GIE bit is cleared
• Current Program Counter (PC) is pushed onto the
• Critical registers are automatically saved to the
• PC is loaded with the interrupt vector 0004h
The firmware within the Interrupt Service Routine (ISR)
should determine the source of the interrupt by polling
the interrupt flag bits. The interrupt flag bits must be
cleared before exiting the ISR to avoid repeated
interrupts. Because the GIE bit is cleared, any interrupt
that occurs while executing the ISR will be recorded
through its interrupt flag, but will not cause the
processor to redirect to the interrupt vector.
The RETFIE instruction exits the ISR by popping the
previous address from the stack, restoring the saved
context from the shadow registers and setting the GIE
bit.
For additional information on a specific interrupt’s
operation, refer to its peripheral chapter.
 2011 Microchip Technology Inc.
event(s)
Enable bit of the interrupt event is contained in the
PIEx register)
stack
shadow registers (See
Context
Note 1: Individual interrupt flag bits are set,
2: All interrupts will be ignored while the GIE
Operation
Saving”)
regardless of the state of any other
enable bits.
bit is cleared. Any interrupt occurring
while the GIE bit is clear will be serviced
when the GIE bit is set again.
Section 8.5 “Automatic
Preliminary
8.2
Interrupt latency is defined as the time from when the
interrupt event occurs to the time code execution at the
interrupt vector begins. The latency for synchronous
interrupts is 3 or 4 instruction cycles. For asynchronous
interrupts, the latency is 3 to 5 instruction cycles,
depending on when the interrupt occurs. See
and
Figure 8-4
Interrupt Latency
PIC12F/LF1840
for more details.
DS41441A-page 79
Figure 8-3