MC68HC08AS32 Datasheet, PDF (176/394 Pages) Motorola, Inc – M68HC08 Family of 8-bit microcontroller units (MCUs)

External Interrupt (IRQ)
14.4 Functional Description
A logic 0 applied to the external interrupt pin can latch a CPU interrupt
request. Figure 14-1 shows the structure of the IRQ module.
Interrupt signals on the IRQ pin are latched into the IRQ latch. An
interrupt latch remains set until one of the following actions occurs:
• Vector fetch — A vector fetch automatically generates an interrupt
acknowledge signal that clears the latch that caused the vector
fetch.
• Software clear — Software can clear an interrupt latch by writing
to the appropriate acknowledge bit in the interrupt status and
control register (ISCR). Writing a logic 1 to the ACK bit clears the
IRQ latch.
• Reset — A reset automatically clears both interrupt latches.
ACK
VECTOR
FETCH
DECODER
IRQ
V_DD
CLR
D
Q
CK
IRQ
LATCH
SYNCHRO-
NIZER
IMASK
MODE
HIGH
VOLTAGE
DETECT
Figure 14-1. IRQ Block Diagram
TO CPU FOR
BIL/BIH
INSTRUCTIONS
IRQF
IRQ
INTERRUPT
REQUEST
TO MODE
SELECT
LOGIC
Advance Information
176
External Interrupt (IRQ)
MC68HC08AS32 — Rev. 3.0
MOTOROLA