mc68hc05p18a Freescale Semiconductor, Inc, mc68hc05p18a Datasheet - Page 43

• Manufacturer Part Number: mc68hc05p18a
• Description: Mc68hc05p18a Hcmos Microcontroller Unit
• Manufacturer: Freescale Semiconductor, Inc

4.4.3 Hardware Interrupts
4.4.3.1 External Interrupt (IRQ)
4.4.3.2 Input Capture Interrupt
MC68HC05P18A
NOTE:
All hardware interrupts are maskable by the I bit in the CCR. If the I bit
is set, all hardware interrupts (internal and external) are disabled.
Clearing the I bit enables the hardware interrupts.
The four hardware interrupts are explained here:
The IRQ pin drives an asynchronous interrupt to the CPU. An edge
detector flip-flop is latched on the falling edge of IRQ. If either the output
from the internal edge detector flip-flop or the level on the IRQ pin is low,
a request is synchronized to the CPU to generate the IRQ interrupt. If the
edge-sensitive only mask option is selected, the output of the internal
edge detector flip-flop is sampled and the input level on the IRQ pin is
ignored. If port A interrupts are selected as a mask option, a port A
interrupt uses the same vector. The interrupt service routine address is
specified by the contents of memory locations $3FFA and $3FFB.
The internal interrupt latch is cleared 9 PH2 clock cycles after the
interrupt is recognized (after location $3FFA is read). Therefore, another
external interrupt pulse could be latched during the IRQ service routine.
When the edge- and level-sensitive mask option is selected, the voltage
applied to the IRQ pin must return to the high state before the return-
from-interrupt (RTI) instruction in the interrupt service routine is
executed.
The input capture interrupt is generated by the 16-bit timer as described
in
Section 8. 16-Bit
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Freescale Semiconductor, Inc.
For More Information On This Product,
External interrupt (IRQ)
Input capture interrupt
Output compare interrupt
Timer overflow interrupt
Go to: www.freescale.com
Interrupts
Timer. The input capture interrupt flag is located in
Interrupt Types
Technical Data
Interrupts