NEC PD75P402 Interrupt request flag & interrupt enable flag, Example EI, IE0, Sktclr Irqcsi

CHAPTER 6. INTERRUPT FUNCTIONS

6.3 INTERRUPT CONTROL CIRCUIT HARDWARE

(1) Interrupt request flag & interrupt enable flag

There are four interrupt request flags (IRQ×××) corresponding to the interrupt sources (interrupt: 3, test: 1) as follows.

INT0 interrupt request flag (IRQ0)

INT2 interrupt request flag (IRQ2)

BT interrupt request flag (IRQBT)

Serial interface interrupt request flag (IRQCSI)

An interrupt request flag is set (1) by generation of an interrupt request and cleared (0) automatically by execution of an interrupt service.

There are four interrupt enable flags (IE×××) corresponding to the interrupt request flags as follows. INT0 interrupt enable flag (IE0)

INT2 interrupt enable flag (IE2)

BT interrupt enable flag (IEBT)

Serial interface interrupt enable flag (IECSI)

An interrupt enable flag enables an interrupt when its contents are “1” and disables it when 0.

When an interrupt request flag is set and the interrupt enable flag permits an interrupt, a vectored interrupt request (VRQn) is generated. This signal is also used to release standby mode (HALT mode) (with the exception of VRQ2).

The interrupt request flags and interrupt enable flags are manipulated by bit-handling instructions and 4-bit memory handling instructions. In addition, the interrupt enable flags are manipulated by the EI IE××× instruction and the DI IE××× instruction. The SKTCLR is normally used for interrupt request flag testing.

Example EI	IE0	; INT0 enabled
DI	IEBT	; INTBT disabled
SKTCLR	IRQCSI	; Skip and clear if IRQCSI is 1

When the interrupt request flag is set by an instruction, although no interrupt is generated, a vectored interrupt is executed in the same way as when an interrupt is generated.

With a RESET input, the interrupt request flags and interrupt enable flags are cleared (0) and all interrupts are disabled.

Table 6-2 Interrupt Request Flag Setting Signal

Interrupt Request Flag	Interrupt Request Flag Setting Signal	Interrupt Enable Flag
IRQBT	Set by basic time interval signal from basic interval timer.	IEBT
IRQ0	Set by INT0/P10 pin input signal edge detection. Detected	IE0
	edge is selected by INT0 mode register (IM0).
IRQCSI	Set by serial interface serial data transfer operation	IECSI
	termination signal.
IRQ2	Set by INT2/P12 pin input signal rising edge detection.	IE2

129