MC68HC908AS60ACFN FREESCALE [Freescale Semiconductor, Inc], MC68HC908AS60ACFN Datasheet - Page 120

• Manufacturer Part Number: MC68HC908AS60ACFN
• Description: M68HC08 Microcontrollers
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

System Integration Module (SIM)
9.5.1.1 Hardware Interrupts
A hardware interrupt does not stop the current instruction. Processing of a hardware interrupt begins after
completion of the current instruction. When the current instruction is complete, the SIM checks all pending
hardware interrupts. If interrupts are not masked (I bit clear in the condition code register), and if the
corresponding interrupt enable bit is set, the SIM proceeds with interrupt processing; otherwise, the next
instruction is fetched and executed.
If more than one interrupt is pending at the end of an instruction execution, the highest priority interrupt is
serviced first.
pending upon exit from the original interrupt service routine, the pending interrupt is serviced before the
LDA instruction is executed.
120
I BIT
R/W
IDB
IAB
INTERRUPT
MODULE
Figure 9-11
MC68HC908AZ60A • MC68HC908AS60A • MC68HC908AS60E Data Sheet, Rev. 6
SP – 4
demonstrates what happens when two interrupts are pending. If an interrupt is
INT1
INT2
Figure 9-11
CCR
SP – 3
Figure 9-10. Interrupt Recovery
CLI
LDA
PSHH
PULH
RTI
PSHH
PULH
RTI
A
#$FF
.
SP – 2
Interrupt Recognition Example
X
SP – 1
PC – 1 [7:0]
INT1 INTERRUPT SERVICE ROUTINE
INT2 INTERRUPT SERVICE ROUTINE
SP
PC – 1 [15:8]
PC
OPCODE
PC + 1
OPERAND
BACKGROUND
ROUTINE
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