HD6417615 Hitachi Semiconductor, HD6417615 Datasheet - Page 59

• Manufacturer Part Number: HD6417615
• Description: Hardware Manual
• Manufacturer: Hitachi Semiconductor

2.2
2.2.1
Register operand data size is always longword (32 bits). When loading data from memory into a
register, if the memory operand is a byte (8 bits) or a word (16 bits), it is sign-extended into a
longword, then loaded into the register.
2.2.2
These formats are classified into bytes, words, and longwords.
Place byte data in any address, word data from 2n addresses, and longword data from 4n
addresses. An address error will occur if accesses are made from any other boundary. In such
cases, the access results cannot be guaranteed. In particular, the stack area referred to by the
hardware stack pointer (SP, R15) stores the program counter (PC) and status register (SR) as
longwords, so establish the hardware stack pointer so that a 4n value will always result.
To enable sharing of the processor accessing memory in little-endian mode and memory, the CS2,
4 space (area 2, 4) has a function that allows access in little-endian mode. The order of byte data
differs between little-endian mode and normal big-endian mode.
Address 2n
Address 4n
Data Formats
Data Format in Registers
Data Formats in Memory
Address m
31
Byte
Word
Address m + 1
23
Byte
Big endian
31
Longword
Address m + 2
Figure 2.6 Data Formats in Memory
15
Figure 2.5 Register Data Format
Byte
Address m + 3
Word
7
Byte
0
Longword
Address m + 3
31
Byte
Word
Address m + 2
23
Little endian
Byte
Longword
Address m + 1
15
Byte
0
Word
Address m
7
Byte
0
Address 2n
Address 4n
41