mc68hc908gr8vp Freescale Semiconductor, Inc, mc68hc908gr8vp Datasheet - Page 48

• Manufacturer Part Number: mc68hc908gr8vp
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Resets and Interrupts
After every instruction, the CPU checks all pending interrupts if the I bit is not set. If more than one
interrupt is pending when an instruction is done, the highest priority interrupt is serviced first. In the
example shown in
pending interrupt is serviced before the LDA instruction is executed.
The LDA opcode is prefetched by both the INT1 and INT2 RTI instructions. However, in the case of the
INT1 RTI prefetch, this is a redundant operation.
48
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, save the H
register and then restore it prior to exiting the routine.
Figure
4-4, if an interrupt is pending upon exit from the interrupt service routine, the
INT1
INT2
MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7
Figure 4-4
CLI
LDA
PSHH
PULH
RTI
PSHH
PULH
RTI
#$FF
.
Interrupt Recognition Example
NOTE
INT1 INTERRUPT SERVICE ROUTINE
INT2 INTERRUPT SERVICE ROUTINE
BACKGROUND
ROUTINE
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