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Rev. 1.0, 07/01, page 29 of 372
Register Indirect with Displacement—@(d:16, ERn) or @(d:24, ERn)
A 16-bit or 24-bit displacement contained in the instruction is added to an address register (ERn)
specified by the register field of the instruction, and the lower 24 bits of the sum the address of a
memory operand. A 16-bit displacement is sign-extended when added.
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 contains 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 the 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 is 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 the word or longword access, the register value
should be even.
Absolute Address—@aa:8, @aa:16, @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), 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.
The access ranges of absolute addresses for the series of this LSI are those shown in table 2-11,
because the upper 8 bits are ignored.
Table 2-11 Absolute Address Access Ranges
Absolute Address Access Range
8 bits (@aa:8) H'FF00 to H'FFFF
16 bits (@aa:16) H'0000 to H'FFFF
24 bits (@aa:24) H'0000 to H'FFFF
Immediate—#xx:8, #xx:16, or #xx:32