H8S2194 Datasheet, PDF (83/1078 Pages) Renesas Technology Corp – Renesas 16-Bit Single-Chip Microcomputer

Section 2 CPU
(2) Register Indirect⎯@ERn
The register field of the instruction code specifies an address register (ERn) which contains the
address of the operand in memory. If the address is a program instruction address, the lower 24
bits are valid and the upper 8 bits are all assumed to be 0 (H'00).
(3) Register Indirect with Displacement⎯@(d:16, ERn) or @(d:32, ERn)
A 16-bit or 32-bit displacement contained in the instruction is added to an address register (ERn)
specified by the register field of the instruction, and the sum gives 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) which contains the
address of a memory operand. After the operand is accessed, 1, 2, or 4 is added to the address
register contents 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 result becomes 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 register value should be even.
(5) Absolute Address⎯@aa:8, @aa:16, @aa:24, or @aa:32
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), or 32 bits long
(@aa:32).
To access data, the absolute address should be 8 bits (@aa:8), 16 bits (@aa:16), or 32 bits
(@aa:32) long. For an 8-bit absolute address, the upper 24 bits are all assumed to be 1 (H'FFFF).
For a 16-bit absolute address the upper 16 bits are a sign extension. A 32-bit absolute address can
access the entire address space.
A 24-bit absolute address (@aa:24) indicates the address of a program instruction. The upper 8
bits are all assumed to be 0 (H'00).
Table 2.12 indicates the accessible absolute address ranges.
Rev.3.00 Jan. 10, 2007 page 47 of 1038
REJ09B0328-0300