Renesas SH7124 R5F7124, Hardware Manual

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Section 2 CPU
Rev. 3.00 Sep. 27, 2007 Page 22 of 758
REJ09B0243-0300
2.3 Data Formats
2.3.1 Register Data Format
The size of register operands is always longwords (32 bits). When loading byte (8 bits) or word
(16 bits) data in memory into a register, the data is sign-extended to longword and stored in the
register.
Longword
31 0
Figure 2.2 Register Data Format
2.3.2 Memory Data Formats
Memory data formats are classified into bytes, words, and longwords. Byte data can be accessed
from any address. Locate, however, word data at an address 2n, longword data at 4n. Otherwise,
an address error will occur if an attempt is made 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, pointed 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.
Byte Byte Byte Byte
Word Word
Longword
31 23
15 7
Address m + 1
Address 2n
Address 4n
Address m
Address m + 3
Address m + 2
0
Figure 2.3 Memory Data Format