MC68HC908LB8_05 Datasheet, PDF (167/234 Pages) Freescale Semiconductor, Inc – M68HC08 Microcontrollers

Interrupts
CLI
LDA #$FF
INT1
PSHH
PULH
RTI
BACKGROUND
ROUTINE
INT1 INTERRUPT SERVICE ROUTINE
INT2
PSHH
INT2 INTERRUPT SERVICE ROUTINE
PULH
RTI
Figure 16-4. Interrupt Recognition Example
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.
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, save the H
register and then restore it prior to exiting the routine.
See Figure 16-5 for a flowchart depicting interrupt processing.
16.3.2 Sources
The sources in Table 16-1 can generate CPU interrupt requests.
MC68HC908LB8 Data Sheet, Rev. 1
Freescale Semiconductor
167