mc68hc908lb8 Freescale Semiconductor, Inc, mc68hc908lb8 Datasheet - Page 82

• Manufacturer Part Number: mc68hc908lb8
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

External Interrupt (IRQ)
When an interrupt pin is both falling-edge and low-level triggered, the interrupt remains set until both of
these events occur:
The vector fetch or software clear may occur before or after the interrupt pin returns to logic 1. As long as
the pin is low, the interrupt request remains pending. A reset will clear the latch and the MODE control bit,
thereby clearing the interrupt even if the pin stays low.
When set, the IMASK bit in the INTSCR masks all external interrupt requests. A latched interrupt request
is not presented to the interrupt priority logic unless the IMASK bit is clear.
8.4 IRQ Pin
A logic 0 on the IRQ pin can latch an interrupt request into the IRQ latch. A vector fetch, software clear,
or reset clears the IRQ latch.
82
$001D
Addr.
•
•
IRQPUD
Vector fetch or software clear
Return of the interrupt pin to logic 1
IRQ
IRQ Status and Control
Register Name
Register (INTSCR)
DECODER
VECTOR
The interrupt mask (I) in the condition code register (CCR) masks all
interrupt requests, including external interrupt requests.
RESET
FETCH
ACK
V
See page 84.
DD
INTERNAL
PULLUP
DEVICE
Reset:
Read:
Write:
V
MODE
Figure 8-1. IRQ Module Block Diagram
DD
Figure 8-2. IRQ I/O Register Summary
D
Bit 7
CK
0
0
MC68HC908LB8 Data Sheet, Rev. 1
CLR
IRQ
FF
Q
= Unimplemented
6
0
0
NOTE
5
0
0
IMASK
SYNCHRO-
VOLTAGE
DETECT
4
0
0
NIZER
HIGH
IRQF
3
0
ACK
IRQF
2
0
0
Freescale Semiconductor
IMASK
1
0
TO CPU FOR
BIL/BIH
INSTRUCTIONS
IRQ
INTERRUPT
REQUEST
TO MODE
SELECT
LOGIC
MODE
Bit 0
0