MC68HC08XL36 Datasheet, PDF (61/362 Pages) Freescale Semiconductor, Inc – HCMOS Microcontroller Unit

Freescale Semiconductor, Inc.
Resets and Interrupts
Interrupts
• Sets the interrupt mask (I bit) to prevent additional interrupts.
Once an interrupt is latched, no other interrupt can take
precedence, regardless of its priority.
• Loads the program counter with a user-defined vector address.
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. If an interrupt is
pending upon exit from the interrupt service routine, the pending
interrupt is serviced before the LDA instruction is executed.
CLI
LDA #$FF
BACKGROUND
ROUTINE
INT1
PSHH
PULH
RTI
INT1 INTERRUPT SERVICE ROUTINE
INT2
PSHH
PULH
RTI
INT2 INTERRUPT SERVICE ROUTINE
Figure 5. 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.
7-ri24_e
MOTOROLA
Resets and Interrupts
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MC68HC08XL36
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