Special Function Registers (Sfrs) - NEC 78K0 Series User Manual

3.2.3 Special function registers (SFRs)

Unlike a general-purpose register, each special function register has a special function.
SFRs are allocated to the FF00H to FFFFH area.
Special function registers can be manipulated like general-purpose registers, using operation, transfer, and bit
manipulation instructions. The manipulatable bit units, 1, 8, and 16, depend on the special function register type.
Each manipulation bit unit can be specified as follows.
• 1-bit manipulation
Describe the symbol reserved by the 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 by the 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 by the assembler for the 16-bit manipulation instruction operand (sfrp).
When specifying an address, describe an even address.
Table 3-6 gives a list of the special function registers. The meanings of items in the table are as follows.
• Symbol
Symbol indicating the address of a special function register. It is a reserved word in the RA78K0, and is defined
as an sfr variable using the #pragma sfr directive in the CC78K0. When using the RA78K0, ID78K0-QB, and
SM+ for 78K0/KX2, symbols can be written as an instruction operand.
• R/W
Indicates whether the corresponding special function register can be read or written.
R/W: Read/write enable
R: Read only
W: Write only
• Manipulatable bit units
Indicates the manipulatable bit unit (1, 8, or 16). "−" indicates a bit unit for which manipulation is not possible.
• After reset
Indicates each register status upon reset signal generation.
72
CHAPTER 3 CPU ARCHITECTURE
Preliminary User's Manual U17260EJ3V1UD