H8S2245 datasheet(91/818 Pages) RENESAS

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Section 2 CPU

Rev.3.00 Mar. 26, 2007 Page 49 of 772

REJ09B0355-0300

2.6.4

Basic Instruction Formats

The H8S/2245 Group 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).

Figure 2.12 shows examples of instruction formats.

NOP, RTS, etc.

ADD.B Rn, Rm, etc.

MOV.B @(d:16, Rn), Rm, etc.

(1) Operation field only

(2) Operation field and register fields

(3) Operation field, register fields, and effective address extension

EA (disp)

(4) Operation field, effective address extension, and condition field

EA (disp)

BRA d:16, etc

Figure 2.12 Instruction Formats (Examples)

(1) 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 four bits of

the instruction. Some instructions have two operation fields.

(2) 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.

(3) Effective Address Extension: Eight, 16, or 32 bits specifying immediate data, an absolute

address, or a displacement.

(4) Condition Field: Specifies the branching condition of Bcc instructions.

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