Datasheet

System Integration Module (SIM)
Exception Control
MC68HC908QY4•MC68HC908QT4•MC68HC908QY2•MC68HC908QT2•MC68HC908QY1•MC68HC908QT1
MOTOROLA System Integration Module (SIM) 89
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Figure 7-11. Interrupt Recognition Example
The LDA opcode is prefetched by both the INT1 and INT2
return-from-interrupt (RTI) instructions. However, in the case of the INT1
RTI prefetch, this is a redundant operation.
NOTE: To maintain compatibility with the M6805 Family, the H register is not
pushed on the stack during interrupt entry. If the interrupt service routine
modifies the H register or uses the indexed addressing mode, software
should save the H register and then restore it prior to exiting the routine.
7.7.1.2 SWI Instruction
The SWI instruction is a non-maskable instruction that causes an
interrupt regardless of the state of the interrupt mask (I bit) in the
condition code register.
NOTE: A software interrupt pushes PC onto the stack. A software interrupt does
not push PC – 1, as a hardware interrupt does.
CLI
LDA
INT1
PULH
RTI
INT2
BACKGROUND ROUTINE#$FF
PSHH
INT1 INTERRUPT SERVICE ROUTINE
PULH
RTI
PSHH
INT2 INTERRUPT SERVICE ROUTINE