NEC mPD789101, User Manual

Page: 69 / 265

User’s Manual U13045EJ2V0UM00
69
CHAPTER 4 CPU ARCHITECTURE
4.4.4 Register addressing
[Function]
General registers are accessed as operands. The general register to be accessed is specified with the register
specify code and functional name in the instruction code.
Register addressing is carried out when an instruction with the following operand format is executed. When
an 8-bit register is specified, one of the eight registers is specified with 3 bits in the instruction code.
[Operand format]
Identifier Description
r X, A, C, B, E, D, L, H
rp AX, BC, DE, HL
‘r’ and ‘rp’ can be described with absolute names (R0 to R7 and RP0 to RP3) as well as function names (X,
A, C, B, E, D, L, H, AX, BC, DE, and HL).
[Description example]
MOV A, C; When selecting the C register for r
Instruction code 0 0 0 0 1 0 1 0
0 0 1 0 0 1 0 1
Register specify code
INCW DE; When selecting the DE register pair for rp
Instruction code 1 0 0 0 1 0 0 0
Register specify code