HD404654 Datasheet, PDF (92/111 Pages) Hitachi Semiconductor – 4-Bit Single-Chip Microcomputer

HD404654 Series
Addressing Modes
RAM Addressing Modes
The MCU has three RAM addressing modes, as shown in figure 75 and described below.
Register Indirect Addressing Mode: The contents of the W, X, and Y registers (10 bits in total) are used
as a RAM address.
Direct Addressing Mode: A direct addressing instruction consists of two words. The first word contains
the opcode, and the contents of the second word (10 bits) are used as a RAM address.
Memory Register Addressing Mode: The memory registers (MR), which are located in 16 addresses
from $040 to $04F, are accessed with the LAMR and XMRA instructions.
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 Direct Addressing
1st word of Instruction
Opcode
2nd word of Instruction
d ₉ d ₈ d₇ d₆ d ₅ d ₄ d₃ d₂ d₁ d₀
RAM address AP₉ AP₈ AP₇ AP₆ AP₅ AP₄ AP₃ AP₂ AP₁ AP₀
Direct Addressing
Instruction
Opcode
m₃ m₂ m₁ m ₀
000100
RAM address AP₉ AP₈ AP₇ AP₆ AP₅ AP₄ AP₃ AP₂ AP₁ AP₀
Memory Register Addressing
Figure 75 RAM Addressing Modes
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