MB89997 datasheet(18/42 Pages) FUJITSU

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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

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).

16 bits

: Program counter

: Accumulator

: Temporary accumulator

: Index register

: Extra pointer

: Stack pointer

: Program status

FFFDH

Indeterminate

I-flag = 0, IL1, 0 = 11

The other bit values are indeterminate.

Initial value

• Structure of the Program Status Register

Vacancy

IL1, 0

9876

3210

CCR

Vacancy Vacancy

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