MC68HC708MP16 Datasheet, PDF (340/398 Pages) Freescale Semiconductor, Inc – Microcontrollers

External Interrupt (IRQ)
17.4 Functional Description
A logic 0 applied to any of the external interrupt pins can latch a CPU
interrupt request. Figure 17-1 shows the structure of the IRQ module.
Interrupt signals on the IRQ1/V_PP pin are latched into the IRQ1 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 ACK1 bit clears the
IRQ1 latch.
• Reset — A reset automatically clears both interrupt latches.
IRQ1/V_PP
V_DD
ACK1
D ^CLR Q
CK
IRQ1
LATCH
SYNCHRO-
NIZER
IMASK1
MODE1
HIGH
VOLTAGE
DETECT
Figure 17-1. IRQ Module Block Diagram
IRQ1
INTERRUPT
REQUEST
TO MODE
SELECT
LOGIC
Addr.
$001E
Name
Bit 7 6
5
4
3
Read: 0
0
0
IRQ Status and Control
Register (ISCR)
Write:
Reset: 0
0
0
0
IRQ1F
0
0
Figure 17-2. IRQ I/O Register Summary
2
0
ACK1
0
1 Bit 0
IMASK1 MODE1
0
0
Technical Data
340
External Interrupt (IRQ)
MC68HC708MP16 — Rev. 3.1
Freescale Semiconductor