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

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CHAPTER 6. INTERRUPT FUNCTIONS

6.6 INTERRUPT APPLICATIONS

When the interrupt function is used, the following setting are first carried out in the main program.

➀ The interrupt enable flag corresponding to the interrupt to be used is set to “1” (EI IE××× instruction).

➁ If INT0 is used, the active edge is selected (IM0 setting).

➂ The interrupt master enable flag (IME) is set to “1” (EI instruction).

Return from the interrupt service program is by means of an RETI instruction.

(1) Interrupt enabling/disabling

➀ Reset

➁ EI IE0

➁ EI IECSI

➂ EI

➃ DI IE0

➄ DI

INT0 & INTCSI enabled

INTCSI enabled

Interrupts disabled

<Main Program>

➀ All interrupts disabled by RESET input.

➁ Interrupt enable flag set by EI IE××× instruction.

At this stage, all interrupts are still disabled.

➂ Interrupt master enable flag set by EI instruction.

At this stage, INT0 & INTCSI are enabled.

Interrupt enable flag cleared by DI IE××× instruction; INT0 disabled.

➄ All interrupts disabled by DI instruction.