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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-
extended to 24 bits and added to the 24-bit PC contents to generate a 24-bit branch address. The
PC value to which the displacement is added is the address of the first byte of the next instruction,
so the possible branching range is –126 to +128 bytes (–63 to +64 words) or –32766 to +32768
bytes (–16383 to +16384 words) from the branch instruction. The resulting value should be an
even number.
8 Memory Indirect—@@aa:8: This mode can be used by the JMP and JSR instructions. The
instruction code contains an 8-bit absolute address specifying a memory operand. This memory
operand contains a branch address. The memory operand is accessed by longword access. The first
byte of the memory operand is ignored, generating a 24-bit branch address. See figure 2.10. The
upper bits of the 8-bit absolute address are assumed to be 0 (H'0000), so the address range is 0 to
255 (H'0000 to H'00FF). Note that the first part of this range is also the exception vector area.
Dummy
Specified by @aa:8
Branch address
Figure 2.10 Memory-Indirect Branch Address Specification
2.6.2
Effective Address Calculation
Table 2.11 explains how an effective address (EA) is calculated in each addressing mode. In the
H8/3664 Series, the upper 8 bits of the calculated address are ignored in order to generate a 16-bit
effective address.
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