MC68HC908GR16 Datasheet, PDF (149/310 Pages) Motorola, Inc – Microcontrollers

Freescale Semiconductor, Inc.
Resets and Interrupts
Interrupts
13.3 Interrupts
13.3.1 Effects
An interrupt temporarily changes the sequence of program execution to respond to
a particular event. An interrupt does not stop the operation of the instruction being
executed, but begins when the current instruction completes its operation.
An interrupt:
• Saves the CPU registers on the stack. At the end of the interrupt, the RTI
instruction recovers the CPU registers from the stack so that normal
processing can resume.
• 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
5
4
STACKING ³
ORDER ₂
1
•
•
•
CONDITION CODE REGISTER
ACCUMULATOR
INDEX REGISTER (LOW BYTE)⁽¹⁾
PROGRAM COUNTER (HIGH BYTE)
PROGRAM COUNTER (LOW BYTE)
•
•
•
1
2
3 _UNSTACKING
4
ORDER
5
$00FF DEFAULT ADDRESS ON RESET
1. High byte of index register is not stacked.
Figure 13-3. Interrupt Stacking Order
MC68HC908GR16 — Rev. 1.0
MOTOROLA
Resets and Interrupts
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Data Sheet
149