H8SLASH3021 datasheet(66/712 Pages) RENESAS

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2. CPU

Rev.2.00 Mar. 22, 2007 Page 42 of 684

REJ09B0352-0200

2 Register Indirect—@ERn: The register field of the instruction code specifies an address

3 Register Indirect with Displacement—@(d:16, ERn) or @(d:24, ERn): A 16-bit or 24-bit

displacement contained in the instruction code is added to the contents of an address register

(ERn) specified by the register field of the instruction, and the lower 24 bits of the sum specify the

address of a memory operand. A 16-bit displacement is sign-extended when added.

4 Register Indirect with Post-Increment or Pre-Decrement—@ERn+ or @–ERn:

• Register indirect with post-increment—@ERn+

The register field of the instruction code specifies an address register (ERn) the lower 24 bits

of which contain the address of a memory operand. After the operand is accessed, 1, 2, or 4 is

added to the address register contents (32 bits) and the sum is stored in the address register.

The value added is 1 for byte access, 2 for word access, or 4 for longword access. For word or

longword access, the register value should be even.

• Register indirect with pre-decrement—@–ERn

The value 1, 2, or 4 is subtracted from an address register (ERn) specified by the register field

in the instruction code, and the lower 24 bits of the result become the address of a memory

operand. The result is also stored in the address register. The value subtracted is 1 for byte

access, 2 for word access, or 4 for longword access. For word or longword access, the resulting

5 Absolute Address—@aa:8, @aa:16, or @aa:24: The instruction code contains the absolute

address of a memory operand. The absolute address may be 8 bits long (@aa:8), 16 bits long

(@aa:16), or 24 bits long (@aa:24). For an 8-bit absolute address, the upper 16 bits are all

assumed to be 1 (H'FFFF). For a 16-bit absolute address the upper 8 bits are a sign extension. A

24-bit absolute address can access the entire address space. Table 2.12 indicates the accessible

address ranges.

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