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CHAPTER 3 INTERRUPT
❍ Interrupt processing time (θ machine cycles)
After the CPU accepts an interrupt request, the CPU saves the dedicated registers in the
system stack and fetches the interrupt vector. The interrupt processing time is thus derived from
the following formula:
At interrupt start: θ = 24 + 6 x Z machine cycles
•
At interrupt return: θ = 11 + 6 x Z machine cycles (RETI instruction)
•
The interrupt processing time differs depending on the address indicated by the stack pointer.
Table 3.4-3 lists correction values (Z) for interrupt processing times.
One machine cycle corresponds to a clock interval of machine clocks (φ).
Table 3.4-3 Correction values (Z) for interrupt processing times
External 8 bits
External even address
External odd address
Internal even address
Internal odd address
64
Address pointed by stack pointer
Correction value (Z)
+4
+1
+4
0
+2
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