HD404019R Datasheet, PDF (46/65 Pages) Renesas Technology Corp – CMOS 4-bit single-chip microcomputers

HD404019R Series
Addressing Modes
RAM Addressing Modes
As shown in figure 22, the MCU has three RAM addressing modes: register indirect addressing, direct
addressing, and memory register addressing.
W register X register
Y register
W₁ W₀ X₃ X₂ X₁ X₀ Y₃ Y₂ Y₁ Y₀
RAM address AP₉ AP₈ AP₇ AP₆ AP₅ AP₄ AP₃ AP₂ AP₁ AP₀
Register Indirect Addressing
Instruction 1st word
Opcode
Instruction 2nd word
d₉ d₈ d₇ d₆ d₅ d₄ d₃ d₂ d₁ d₀
RAM address AP₉ AP₈ AP₇ AP₆ AP₅ AP₄ AP₃ AP₂ AP₁ AP₀
Direct Addressing
Instruction
Opcode
m₃ m₂ m₁ m₀
0 0 0 01 0
RAM address AP₉ AP₈ AP₇ AP₆ AP₅ AP₄ AP₃ AP₂ AP₁ AP₀
Memory Register Addressing
Figure 22 RAM Addressing Modes
Register Indirect Addressing Mode: The W register, X register, and Y register contents (10 bits) are
used as the RAM address.
Direct Addressing Mode: A direct addressing instruction consists of two words, with the word (10 bits)
following the opcode used as the RAM address.
Memory Register Addressing Mode: The memory registers (16 digits from $020 to $02F) are accessed
by executing the LAMR and XMRA instructions.
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