UPD17010GF datasheet(85/424 Pages) NEC

85 / 424 page

µPD17010

10.4 Stack Pointer, Address Stack Register, and Program Counter

The address stack register saves a return address from which program execution is resumed when execution has

returned from an interrupt processing routine.

The stack pointer specifies the address of an address stack register.

When an interrupt has been accepted, the value of the stack pointer is decremented by one, and the value of the

program counter at that time is saved to the address stack register specified by the stack pointer.

When a dedicated return instruction “RETI” is executed after the processing of the interrupt processing routine has

been completed, the contents of the address stack register specified by the stack pointer are restored to the program

counter, and the value of the stack pointer is incremented by one.

For more information, refer to 3. ADDRESS STACK (ASK).

10.5 Interrupt Enable Flip-Flop (INTE)

The interrupt enable flip-flop enables all the interrupts.

When this flip-flop is set, all the interrupts are enabled. When it is reset, all the interrupts are disabled.

To set or reset this flip-flop, a dedicated instruction, “EI (to set)” or “DI (to reset)”, is used.

The “EI” instruction sets this flip-flop when the next instruction is executed, and the “DI” instruction resets the flip-

flop during its execution.

When an interrupt is accepted, this flip-flop is automatically reset.

Even if the “DI” instruction is executed in the DI status, or if the “DI” instruction is executed in the EI status, nothing

is affected.

This flip-flop is reset at power-ON reset or CE reset, and when the clock stop instruction is executed.

UPD17010GF Datasheet(PDF) 85 Page - NEC