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CHAPTER 3 CPU ARCHITECTURE
15
0
SFR
Effective Address
1
111111
87
07
OP code
sfr-offset
1
3.4.5 Special-Function Register (SFR) addressing
[Function]
The memory-mapped special-function register (SFR) is addressed with 8-bit immediate data in an instruction
word.
This addressing is applied to the 240-byte spaces FF00H to FFCFH and FFE0H to FFFFH. However, the SFR
mapped at FF00H to FF1FH can be accessed with short direct addressing.
[Operand format]
Identifier Description
sfr Special-function register name
sfrp 16-bit manipulatable special-function register name (even address only)
[Description example]
MOV PM0, A; when selecting PM0 (FF20H) as sfr
Operation code 1 1 1 1 0 1 1 0 OP code
0 0 1 0 0 0 0 0 20H (sfr-offset)
[Illustration]