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CHAPTER 5 CPU ARCHITECTURE
5.2.3 Special function registers (SFRs)
Unlike the general-purpose registers, special function registers have their own functions and are allocated to an
area of addresses FF00H-FFFFH.
The special function registers can also be manipulated in the same manner as the general-purpose registers by
using operation, transfer, and bit manipulation instructions. The bit units in which one register is to be manipulated
(1, 8, or 16 bits) differ from that of another register.
The bit unit for manipulation is specified as follows:
1-bit manipulation
A symbol reserved by the assembler is written as the operand (sfr.bit) of a 1-bit manipulation instruction. An
address can also be specified.
8-bit manipulation
A symbol reserved by the assembler is written as the operand (sfr) of an 8-bit manipulation instruction. An
address can also be specified.
16-bit manipulation
A symbol reserved by the assembler is written as the operand (sfrp) of a 16-bit manipulation instruction. To
specify address, write an even address.
Table 5-7 lists the special function register. The meanings of the symbols in this table are as follows:
Symbol
These symbols indicate the addresses of the special function registers. They are reserved words for the RA78K/
0 and defined by header file sfrbit.h for the CC78K/0. These symbols can be written as the operands of
instructions when the RA78K/0, ID78K0-NS, ID78K0, or SM78K0 is used.
R/W
Indicates whether the special function register in question can be read or written.
R/W : Read/write
R
: Read only
W
: Write only
Bit units for manipulation
indicates the bit units (1, 8, 16) in which the special function register in question can be manipulated. – indicates
the bit units that cannot be manipulated.
At reset
Indicates the status of the special function register when the RESET signal is input.