58
2.7
Addressing Modes and Effective Address Calculation
2.7.1
Addressing Mode
The CPU supports the eight addressing modes listed in table 2-4. Each instruction uses a subset of
these addressing modes. Arithmetic and logic instructions can use the register direct and
immediate modes. Data transfer instructions can use all addressing modes except program-counter
relative and memory indirect. Bit manipulation instructions use register direct, register indirect, or
absolute addressing mode to specify an operand, and register direct (BSET, BCLR, BNOT, and
BTST instructions) or immediate (3-bit) addressing mode to specify a bit number in the operand.
Table 2-4
Addressing Modes
No.
Addressing Mode
Symbol
1
Register direct
Rn
2
Register indirect
@ERn
3
Register indirect with displacement
@(d:16,ERn)/@(d:32,ERn)
4
Register indirect with post-increment
Register indirect with pre-decrement
@ERn+
@–ERn
5
Absolute address
@aa:8/@aa:16/@aa:24/@aa:32
6
Immediate
#xx:8/#xx:16/#xx:32
7
Program-counter relative
@(d:8,PC)/@(d:16,PC)
8
Memory indirect
@@aa:8
(1) Register Direct—Rn: The register field of the instruction specifies an 8-, 16-, or 32-bit
general register containing the operand. R0H to R7H and R0L to R7L can be specified as 8-bit
registers. R0 to R7 and E0 to E7 can be specified as 16-bit registers. ER0 to ER7 can be specified
as 32-bit registers.
(2) Register Indirect—@ERn: The register field of the instruction code specifies an address
register (ERn) which contains the address of the operand on 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.
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