NEC PD754144 User Manual page 209

(5) Executing pending interrupt - two interrupts with lower priority occur simultaneously -
EI
EI
EI
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
<1> If INT0 and INTT0 with a lower priority occur at the same time (while the same instruction is being
executed), INT0 with a higher priority is executed first (INTT0 is held pending).
<2> When the INT0 servicing routine is terminated by the RETI instruction, the pending INTT0 servicing
program is started.
CHAPTER 7 INTERRUPT AND TEST FUNCTIONS
<Main program>
Reset
IET0
IE0
INT0
<1>
INTT0
User's Manual U10676EJ3V0UM
<lNT0 servicing program>
<2> RETI
<lNTT0 servicing program>
RETI
209