NEC PD750008 - Manual (Page 229)

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CHAPTER 6 INTERRUPT AND TEST FUNCTIONS
(7) Enabling of level-two interrupts (enabling level-two INTT0 and INT0 interrupts with INTCSI and INT4
handled as level-one interrupts)
<1> When an INTCSI interrupt not allowed to be a level-two interrupt occurs, the INTCSI service program
starts, and status 1 is set.
<2> Status 0 is set by clearing IST0. INTCSI and INT4 not allowed to be level-two interrupts are disabled.
<3> When INTT0 allowed to be a level-two interrupt occurs, the level-two interrupt is executed, and status
1 is set to disable all interrupts.
<4> When INTT0 processing is completed, status 0 is set again.
<5> INTCSI and INT4 which have been disabled are enabled, then control returns.
Reset
<INTCSI service program>
EI IET0
<Main program>
EI IE0
EI IECSI
Status 0
Status 0
Status 0
Status 1
Status 0
Status 1
<3> INTT0
<2> DI
CLR1 IST0
DI IECSI
DI IE4
EI
<INTT0 service program>
<4> RETI
EI IECSI
EI IE4
RETI
<5>
<1> INTCSI
EI IE4
EI
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