UPD75402ACT datasheet(20/48 Pages) NEC

20 / 48 page

µPD75402A(A)

INTERRUPT FUNCTION

The

µPD75402A(A) has three interrupt sources and each of them has the interrupt vector table.

The

µPD75402A(A) is also provided with one edge-sensitive testable input signal.

When a vectored interrupt request is issued, the PC and PSW are saved in the stack, and the contents of

the vector table which corresponds to the issued vectored interrupt are set in the PC as a start address. The

program branches to the interrupt service routine. These operations are performed automatically by the

hardware.

The flag is set by detecting the edge of the testable input signal, but a vectored interrupt request is not

issued.

During execution of the interrupt service routine, the

µPD75402A(A) does not accept the other interrupt

requests. Unlike the other 75X series, the

µPD75402A(A) cannot handle multiple interrupts.

The interrupt control circuit of the

µPD75402A(A) has the following functions.

• Vectored interrupt function under hardware control which can determine whether to accept an interrupt

by an interrupt enable flag (IE

×××) and an interrupt master enable flag (IME).

• Any interrupt start address can be set.

• Test function of an interrupt request flag (IRQ

×××) (Software can confirm that an interrupt occurs.)

• Release of the standby (HALT) mode (An interrupt to be released by an interrupt enable flag can be selected

from interrupts other than INT0.)

UPD75402ACT Scheda tecnica(PDF) 20 Page - NEC