Special Function Registers (Sfrs) - NEC 78K/0 Series User Manual

2.3 Special Function Registers (SFRs)

Unlike a general-purpose register, each special-function register has a special function.
Special function registers are allocated in the 256-byte area FF00H to FFFFH.
Special function registers can be manipulated, like general-purpose registers, by operation, transfer and bit
manipulation instructions. The manipulatable bit units (1, 8, and 16) differ depending on the special function
register type.
Each manipulation bit unit can be specified as follows.
• 1-bit manipulation
Describes a symbol reserved by the assembler for the 1-bit manipulation instruction operand (sfr.bit). This
manipulation can also be specified by an address.
• 8-bit manipulation
Describes a symbol reserved by the assembler for the 8-bit manipulation instruction operand (sfr). This
manipulation can also be specified by an address.
• 16-bit manipulation
Describes a symbol reserved by the assembler for the 16-bit manipulation instruction operand (sfrp). When
addressing an address, describe an even address.
For details of the special function registers, refer to the user's manual of each product.
Caution Do not access addresses to which SFRs are not allocated. If an address is erroneously
accessed, the CPU may become deadlocked.
CHAPTER 2 REGISTERS
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