NEC PD754144 User Manual page 207

(3) Nesting of interrupts with higher priority (INTBT has higher priority and INTT0 and INTT2 have lower
priority)
Reset
SEL RB2
EI IEBT
EI IET0
EI IET2
MOV A, #9
<1>
MOV IPS, A
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INTT0
<2>
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<1> INTBT is specified as having a higher priority by setting of IPS, and interrupts are enabled at the same
time.
<2> INTT0 servicing program is started when INTT0 with a lower priority occurs. Status 1 is set and the other
interrupts with a lower priority are disabled. RBE = 0 to select register bank 0.
<3> INTBT with a higher priority occurs. The interrupts are nested. The status is changed to 0 and all
interrupts are disabled.
<4> RBE = 1 and RBS = 1 to select register bank 1 (only the registers used may be saved by the PUSH
instruction).
<5> RBS is returned to 2, and execution returns to the main routine. The status is returned to 1.
CHAPTER 7 INTERRUPT AND TEST FUNCTIONS
; RBE = 1, MBE = 0
Status 0
<lNTT0 servicing program>
INTBT
<3>
Status 0
User's Manual U10676EJ3V0UM
; RBE = 0
<lNTBT servicing program>
Status 1
SEL RB1
<4>
Status 2
<5> SEL RB2
RETI
Status 1
RETI
; RBE = 1
207