MB89990 Просмотр технического описания (PDF) - Fujitsu

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производитель

MB89990

8-bit Proprietary Microcontroller

Fujitsu 

MB89990 Series

2. Registers

The F2MC-8L family has two types of registers; dedicated registers in the CPU and general-purpose registers

in the memory. The following dedicated registers are provided:

Program counter (PC):

A 16-bit-long register for indicating the instruction storage positions

Accumulator (A):

A 16-bit-long temporary register for storing arithmetic operations, etc. When the

instruction is an 8-bit data processing instruction, the lower byte is used.

Temporary accumulator (T): A 16-bit-long register which performs arithmetic operations with the accumulator.

When the instruction is an 18-bit data processing instruction, the lower byte is

used.

Index register (IX):

A 16-bit-long register for index modification

Extra pointer (EP) :

A 16-bit-long pointer for indicating a memory address

Stack pointer (SP) :

A 16-bit-long register for indicating a stack area

Program status (PS) :

A 16-bit-long register for storing a register pointer, a condition code

16 bits

PC

A

T

IX

EP

SP

PS

Initial value

: Program counter

FFFDH

: Accumulator

Indeterminate

: Temporary accumulator Indeterminate

: Index register

Indeterminate

: Extra pointer

Indeterminate

: Stack pointer

Indeterminate

: Program status

I-flag = 0, IL1, 0 = 11

The other bit values are indeterminate.

The PS can further be divided into higher 8 bits for use as a register bank pointer (RP) and the lower 8 bits for

use as a condition code register (CCR) (see the diagram below).

• Structure of the Program Status Register

15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0

PS

RP

Vacancy Vacancy Vacancy H

I

IL1, 0

NZVC

RP

CCR

18

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