NEC uPD78P078 - Manual (Page 122)

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CHAPTER 5 CPU ARCHITECTURE
5.4 Operand Address Addressing
The following methods are available to specify the register and memory (addressing) which undergo manipulation
during instruction execution.
5.4.1 Implied addressing
[Function]
The register which functions as an accumulator (A and AX) in the general register is automatically (implicitly)
addressed.
Of the
µ
PD78078 and 78078Y Subseries instruction words, the following instructions employ implied addressing.
Instruction Register to be Specified by Implied Addressing
MULU A register for multiplicand and AX register for product storage
DIVUW AX register for dividend and quotient storage
ADJBA/ADJBS A register for storage of numeric values which become decimal correction targets
ROR4/ROL4 A register for storage of digit data which undergoes digit rotation
[Operand format]
Because implied addressing can be automatically employed with an instruction, no particular operand format is
necessary.
[Description example]
In the case of MULU X
With an 8-bit x 8-bit multiply instruction, the product of A register and X register is stored in AX. In this example,
the A and AX registers are specified by implied addressing.