UPD17217GT datasheet(12/84 Pages) NEC

12 / 84 page

µPD17215, 17216, 17217, 17218

2.3

Stack

A stack is a register to save a program return address and the contents of system registers (to be described later) when

a subroutine is called or when an interrupt is accepted.

2.3.1

Stack configuration

Fig. 2-3 shows the stack configurarion.

A stack consists of a stack pointer (a 4-bit binary counter, the upper 1-bit fixed to 0), five 11-bit (

µPD17215)/12-bit

(

µPD17216)/13-bit (µPD17217, 17218) address stack registers, and three 5-bit (µPD17215, 17216)/6-bit (µPD17217,

17218) interrupt stack registers.

Fig. 2-3

Stack Configuration

Address stack registers

(ASR)

b11

b10

Address stack register 1

Address stack register 2

Address stack register 3

Address stack register 4

SPb2 SPb1 SPb0

Stack pointer

(SP)

Interrupt stack registers

(INTSK)

BANKSK1

BANKSK2

BCDSK0

BCDSK1

BCDSK2

CMPSK0

CMPSK1

CMPSK2

CYSK0

CYSK1

CYSK2

ZSK0

ZSK1

ZSK2

IXESK0

IXESK1

IXESK2

Address stack register 0

WDOUT pin goes low

when the contents

of the stack pinter

are 6H-7H.

b12

PD17215

PD17216

PD17217, 17218

BANKSK0

Undefined

PD17215, 17216

PD17217, 17218

UPD17217GT Datasheet(PDF) 12 Page - NEC

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