SH7708 datasheet(38/633 Pages) RENESAS

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Longword

Byte0 Byte1 Byte2 Byte3

Word1

Big-endian mode

Word0

Address A + 4

Address A + 8

Address A + 4

Address A

Address A + 1 Address A + 3

Byte3 Byte2 Byte1 Byte0

Word0

Little-endian mode

Word1

Address A + 11

Address A + 10 Address A + 8

Address A

Address A + 8

Address A + 9

Address A + 2

Figure 2.7 Byte, Word, and Longword Alignment

2.3

Instruction Features

2.3.1

Execution Environment

Data Length: The SH7708 Series instruction set is implemented with fixed-length 16-bit wide

instructions executed in a pipelined sequence with single-cycle execution for most instructions.

All operations are executed in 32-bit longword units. Memory can be accessed in 8-bit byte, 16-bit

word, or 32-bit longword units, with byte or word units sign-extended into 32-bit longwords.

Literals are sign-extended in arithmetic operations (MOV, ADD, and CMP/EQ instructions) and

zero-extended in logical operations (TST, AND, OR, and XOR instructions).

Load/Store Architecture: The SH7708 Series features a load-store architecture in which basic

operations are executed in registers. Operations requiring memory access are executed in registers

following register loading, except for bit-manipulation operations such as logical AND functions,

which are executed directly in memory.

Delayed Branching: Unconditional branching is implemented as delayed branch operations.

Pipeline disruptions due to branching are minimized by the execution of the instruction following

the delayed branch instruction prior to branching. Conditional branch instructions are of two

kinds, delayed and normal.

BRA

TRGET

ADD

R1, R0

;ADD is executed prior to branching to TRGET

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