MC68HC908GZ8 Datasheet, PDF (264/344 Pages) Motorola, Inc – Microcontrollers

Freescale Semiconductor, Inc.
System Integration Module (SIM)
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). See Figure 20-10.
FROM RESET
I BBIRTESAEKT?
YES
INTERRUPT?
NO
YES
I BIT SET?
NO
IRQ
YES
INTERRUPT?
NO
AS MANY INTERRUPTS
AS EXIST ON CHIP
STACK CPU REGISTERS
SET I BIT
LOAD PC WITH INTERRUPT VECTOR
FETCH NEXT
INSTRUCTION
SWI
YES
INSTRUCTION?
NO
RTI
YES
INSTRUCTION?
NO
UNSTACK CPU REGISTERS
EXECUTE INSTRUCTION
Figure 20-10. Interrupt Processing
Data Sheet
264
System Integration Module (SIM)
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MC68HC908GZ8
MOTOROLA