MC68HC908QY2 MOTOROLA [Motorola, Inc], MC68HC908QY2 Datasheet - Page 86

• Manufacturer Part Number: MC68HC908QY2
• Description: Microcontrollers
• Manufacturer: MOTOROLA [Motorola, Inc]

System Integration Module (SIM)
7.7 Exception Control
7.7.1 Interrupts
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Normal sequential program execution can be changed in three different
ways:
An interrupt temporarily changes the sequence of program execution to
respond to a particular event.
system interrupts.
Interrupts are latched, and arbitration is performed in the SIM at the start
of interrupt processing. The arbitration result is a constant that the CPU
uses to determine which vector to fetch. Once an interrupt is latched by
the SIM, no other interrupt can take precedence, regardless of priority,
until the latched interrupt is serviced (or the I bit is cleared).
At the beginning of an interrupt, the CPU saves the CPU register
contents on the stack and sets the interrupt mask (I bit) to prevent
additional interrupts. At the end of an interrupt, the RTI instruction
recovers the CPU register contents from the stack so that normal
processing can resume.
Figure 7-10
1. Interrupts
2. Reset
3. Break interrupts
a. Maskable hardware CPU interrupts
b. Non-maskable software interrupt instruction (SWI)
System Integration Module (SIM)
shows interrupt recovery timing.
Figure 7-9
Figure 7-8
shows interrupt entry timing.
flow charts the handling of
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