MC68HC908KX8 Datasheet, PDF (90/310 Pages) Motorola, Inc – Microcontrollers

System Integration Module (SIM)
6.6.1.1 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. Figure 6-10
demonstrates what happens when two interrupts are pending. If an
interrupt is pending upon exit from the original interrupt service routine,
the pending interrupt is serviced before the load-accumulator- from-
memory (LDA) instruction is executed.
CLI
LDA #$FF
INT1
PSHH
PULH
RTI
BACKGROUND
ROUTINE
INT1 INTERRUPT SERVICE ROUTINE
INT2
PSHH
PULH
RTI
INT2 INTERRUPT SERVICE ROUTINE
Figure 6-10. Interrupt Recognition Example
Technical Data
90
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 — Rev. 1.0
System Integration Module (SIM)
MOTOROLA