Electronics America 4-Bit Single-Chip Microcomputer User's Manual

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CHAPTER 6. INTERRUPT FUNCTIONS
(2) Example using INTBT, INT0 (falling edge active), and INTCSI
➀ Reset
➁ MOV
MOV
CLR1
➂ EI
EI
EI
EI



➄ RETI
<INT0 Service Program>
➃ INT0
A, #1
IM0, A
IRQ0
IEBT
IE0
IECSI
; MBE = 0
Status 0
Status 1
Status 0
<Main Program>
➀ All interrupts disabled and status 0 set by RESET input.
➁ INT0 set to falling edge active.
➂ Interrupts enabled by EI and EI IE××× instructions.
On fall of INT0, INT0 interrupt service program is started, status is changed to 1 and all interrupts are
disabled.
➄ RETI instruction effects return from interrupt, restores status to 0, and enables interrupts.
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