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CHAPTER 3 CPU ARCHITECTURE
User’s Manual U15104EJ2V0UD
3.2.3 Special Function Registers (SFR)
Unlike a general-purpose register, each special function register has special functions.
SFRs are allocated in the FF00H to FFFFH area.
SFRs are can be manipulated like general-purpose registers, using operation, transfer and bit manipulation
instructions. The manipulatable bit units: 1, 8, and 16, depends on the special function register type.
The manipulatable bit units can be specified as follows.
•
1-bit manipulation
Use the symbol reserved in the assembler for the 1-bit manipulation instruction operand (sfr.bit).
This manipulation can also be specified with an address.
•
8-bit manipulation
Use the symbol reserved in the assembler for the 8-bit manipulation instruction operand (sfr).
This manipulation can also be specified with an address.
•
16-bit manipulation
Use the symbol reserved in the assembler for the 16-bit manipulation instruction operand (sfrp).
When addressing an address, use an even address.
Table 3-4 gives a list of special function registers. The meanings of items in the table are as follows.
•
Symbol
This is a symbol to indicate an address of the special function register.
These symbols are reserved for the DF178054 and RA78K0, and defined by header file sfrbit.h for the CC78K0.
They can be written as instruction operands when the RA78K0, ID78K0, or ID78K0-NS is used.
•
R/W
Indicates whether the corresponding special function register can be read or written.
R/W:
Read/write enable
R:
Read only
R&Reset:
Read only (reset to 0 when read)
W:
Write only
•
Bit units for manipulation
indicates the manipulatable bit units: 1, 8, and 16. – indicates the bit units that cannot be manipulated.
•
After reset
Indicates each register status upon reset. The values of special function registers whose addresses are not
shown in the table are undefined at reset.