SH7018 datasheet(30/431 Pages) RENESAS

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2.2

Data Formats

2.2.1

Data Format in Registers

bits) or a word (16 bits), it is sign-extended into a longword when loaded into a register (figure

2.4).

Longword

Figure 2.4 Longword Operand

2.2.2

Data Format in Memory

Memory data formats are classified into bytes, words, and longwords. Byte data can be accessed

from any address, but an address error will occur if you try to access word data starting from an

address other than 2n or longword data starting from an address other than 4n. In such cases, the

data accessed cannot be guaranteed. The hardware stack area, referred to by the hardware stack

pointer (SP, R15), uses only longword data starting from address 4n because this area holds the

program counter and status register (figure 2.5).

Byte

Word

Address 2n

Address 4n

Longword

Address m

Address m + 2

Address m + 1

Address m + 3

Figure 2.5 Byte, Word, and Longword Alignment

2.2.3

Immediate Data Format

Byte (8-bit) immediate data resides in an instruction code. Immediate data accessed by the MOV,

ADD, and CMP/EQ instructions is sign-extended and handled in registers as longword data.

Immediate data accessed by the TST, AND, OR, and XOR instructions is zero-extended and

handled as longword data. Consequently, AND instructions with immediate data always clear the

upper 24 bits of the destination register.

SH7018 Datasheet(PDF) 30 Page - Renesas Technology Corp