HD6473032F Datasheet, PDF (53/572 Pages) Hitachi Semiconductor – Hitachi Microcomputer

2.6.4 Basic Instruction Formats
The H8/300H instructions consist of 2-byte (1-word) units. An instruction consists of an operation
field (OP field), a register field (r field), an effective address extension (EA field), and a condition
field (cc).
Operation Field: Indicates the function of the instruction, the addressing mode, and the operation
to be carried out on the operand. The operation field always includes the first 4 bits of the
instruction. Some instructions have two operation fields.
Register Field: Specifies a general register. Address registers are specified by 3 bits, data
registers by 3 bits or 4 bits. Some instructions have two register fields. Some have no register
field.
Effective Address Extension: Eight, 16, or 32 bits specifying immediate data, an absolute
address, or a displacement. A 24-bit address or displacement is treated as 32-bit data in which the
first 8 bits are 0 (H'00).
Condition Field: Specifies the branching condition of Bcc instructions.
Figure 2-9 shows examples of instruction formats.
Operation field only
op
Operation field and register fields
op
rn
rm
Operation field, register fields, and effective address extension
op
rn
rm
EA (disp)
Operation field, effective address extension, and condition field
op
cc
EA (disp)
NOP, RTS, etc.
ADD.B Rn, Rm, etc.
MOV.B @(d:16, Rn), Rm
BRA d:8
Figure 2-9 Instruction Formats
38