XC912BC32CFU8 Motorola Semiconductor Products, XC912BC32CFU8 Datasheet - Page 76

• Manufacturer Part Number: XC912BC32CFU8
• Description: M68HC12B Family Data Sheet
• Manufacturer: Motorola Semiconductor Products

Resets and Interrupts
Data Sheet
76
After stacking the CCR, the CPU:
If no other interrupt request is pending at the end of the interrupt service routine, a
return-from-interrupt (RTI) instruction recovers the stacked values. Program
execution resumes program at the return address.
If another interrupt request is pending at the end of an interrupt service routine, the
RTI instruction recovers the stacked values. However, the CPU then:
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Sets the I bit to prevent other interrupts from disrupting the interrupt service
routine
Sets the X bit if an XIRQ interrupt request is pending
Fetches the interrupt vector for the highest-priority request that was pending
at the beginning of the interrupt sequence
Begins execution of the interrupt service routine at the location pointed to by
the vector
Adjusts the stack pointer to point again at the stacked CCR location, SP – 9
Fetches the vector of the pending interrupt
Begins execution of the interrupt service routine at the location pointed to by
the vector
Table 4-3. Stacking Order on Entry to Interrupts
Memory Location
Resets and Interrupts
SP – 2
SP – 4
SP – 6
SP – 8
SP – 9
Stacked Values
RTN
Y
X
B : A
CCR
H
H
H
: RTN
: Y
: X
M68HC12B Family — Rev. 8.0
L
L
L
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