NEC NEC PD78081(A), User Manual

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CHAPTER 3 CPU ARCHITECTURE
3.4.2 Register addressing
[Function]
This addressing accesses a general register as an operand. The general register accessed is specified by the
register bank select flags (RBS0 and RBS1) and register specify code (Rn or RPn) in an 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 operation 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 function names (X, A, C, B, E, D, L, H, AX, BC, DE and HL) as well as absolute
names (R0 to R7 and RP0 to RP3).
[Description example]
MOV A, C; when selecting C register as r
Operation code 0 1 1 0 0 0 1 0
Register specify code
INCW DE; when selecting DE register pair as rp
Operation code 1 0 0 0 0 1 0 0
Register specify code