Zilog Z08470 - Manual (Page 102)

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UM008101-0601 Direct Memory Access
Figure 33. Interrupt Service Routine
Interrupt Latches
Two primary latches are associated with the interrupt structure:
•
Interrupt Pending (IP). Set whenever the DMA requests an interrupt
but has not yet acknowledged. It holds the INT line Low (Figure 34).
•
Interrupt Under Service (IUS). Set when the CPU acknowledges the
DMA interrupt (Figure 35). This accomplishes three things:
– Prevents further interrupts by this DMA
MEMORY CPU DMA
Jump Table I Register Interrupt
Vector
Jump Table
Service Routine
Program
Counter
Program
Counter
Service Routine
Write
Registers
Register
A.
B.
C.