NEC PD17062 - Manual (Page 126)

126
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PD17062
For multiple interrupts of more than two levels, operations of the device and emulator differ as shown in
Figs. 11-8 and 11-9.
At interrupt stack, the device operation is the sweep-off type and the emulator operation is the rotation type.
Use the RET instruction as the last restoration instruction when using multiple interrupts of more than two
levels. RETI and RET instructions operate in the same manner except when restoring the contents of the
interrupt stack.