NEC PD750008 - Manual (Page 228)

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µPD750008 USER'S MANUAL
(6) Executing pending interrupt – interrupt occurs during interrupt processing (INTBT has higher
priority and INTT0 and INTCSI have lower priority) –
<1> When INTBT with the higher priority and INTT0 with the lower priority occur at the same time, the
processing of the interrupt with the higher priority is started (if there is no possibility that an interrupt
with the higher priority occurs while another interrupt with the higher priority is processed, DI IExx
is not necessary).
<2> When an interrupt with the lower priority occurs while the interrupt with the higher priority is executed,
the interrupt with the lower priority is kept pending.
<3> When the interrupt with the higher priority has been processed, INTCSI with the higher priority of
the pending interrupts is executed.
<4> When the processing of INTCSI has been completed, the pending INTT0 is processed.
*
<Main program>
Reset
EI
EI
EI
MOV
MOV IEBT
IET0
IECSI
A, #9
IPS, A
INTT0
RETI
<INTT0 service program >
INTBT
<INTBT service program >
<4> RETI
<INTCSI service program >
<3> RETI
POP rp
PUSH rp
<2> INTCSI
<1>