UPD78044F datasheet(66/472 Pages) NEC

66 / 472 page

Chapter 3

CPU Architecture

User’s Manual U16504EE1V1UD00

3.2.3 Special function register (SFR)

Unlike a general register, each special function register has special functions.

It is allocated in the FF00H to FFFFH area.

The special function registers can be manipulated in a similar way as the general registers, by using

operation, transfer, or bit-manipulate instructions. The special function registers are read from and writ-

ten to in specified manipulation bit units (1, 8, and/or 16) depending on the register type.

Each manipulation bit unit can be specified as follows.

• 1-bit manipulation

Describe the symbol reserved with assembler for the 1-bit manipulation instruction operand

(sfr.bit).

This manipulation can also be specified with an address.

• 8-bit manipulation

Describe the symbol reserved with assembler for the 8-bit manipulation instruction operand

(sfr).

This manipulation can also be specified with an address.

• 16-bit manipulation

Describe the symbol reserved with assembler for the 16-bit manipulation instruction operand

(sfrp).

When addressing an address, describe an even address.

Table 3-5, “Special Function Register List,” on page 67 gives a list of special function regis-

ters. The meaning of items in the table is as follows.

• Symbol

The assembler software RA78K0 translates these symbols into corresponding addresses

where the special function registers are allocated. These symbols should be used as instruction

operands in the case of programming.

• R/W

This column shows whether the corresponding special function register can be read or written.

R/W : Both reading and writing are enabled.

: The value in the register can read out. A write to this register is ignored.

: A value can be written to the register. Reading values from the register is impossible.

• Manipulation

The register can be manipulated in bit units.

• After reset

The register is set to the value immediately after the RESET signal is input.

UPD78044F Datasheet(PDF) 66 Page - NEC