Table of Contents
Advertisement
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
register value should be even.
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.
Table 2.12 Absolute Address Access Ranges
Absolute
Address
8 bits (@aa:8)
16 bits (@aa:16)
24 bits (@aa:24)
6 Immediate—#xx:8, #xx:16, or #xx:32: The instruction code contains 8-bit (#xx:8), 16-bit
(#xx:16), or 32-bit (#xx:32) immediate data as an operand.
The instruction codes of the ADDS, SUBS, INC, and DEC instructions contain immediate data
implicitly. The instruction codes of some bit manipulation instructions contain 3-bit immediate
data specifying a bit number. The TRAPA instruction code contains 2-bit immediate data
specifying a vector address.
7 Program-Counter Relative—@(d:8, PC) or @(d:16, PC): This mode is used in the Bcc and
BSR instructions. An 8-bit or 16-bit displacement contained in the instruction code is sign-
42
1-Mbyte Modes
H'FFF00 to H'FFFFF
(1048320 to 1048575)
H'00000 to H'07FFF,
H'F8000 to H'FFFFF
(0 to 32767, 1015808 to 1048575)
H'00000 to H'FFFFF
(0 to 1048575)
16-Mbyte Modes
H'FFFF00 to H'FFFFFF
(16776960 to 16777215)
H'000000 to H'007FFF,
H'FF8000 to H'FFFFFF
(0 to 32767, 16744448 to 16777215)
H'000000 to H'FFFFFF
(0 to 16777215)
Advertisement
Table of Contents
