Memory Data Formats - Hitachi H8/3664 Hardware Manual

2.4.2

Memory Data Formats

Figure 2.8 shows the data formats on memory. The H8/300H CPU can access word data and
longword data on memory, but word or longword data must begin at an even address. If an attempt
is made to access word or longword data at an odd address, no address error occurs but the least
significant bit of the address is regarded as 0, so the access starts at the preceding address. This
also applies to instruction fetches.
When ER7 (SP) is used as an address register to access the stack, the operand size should be word
size or longword size.
Data Type
1-bit data
Byte data
Word data
Longword data
Address
Address L
Address L
Address 2M
Address 2M + 1
Address 2N
Address 2N + 1
Address 2N + 2
Address 2N + 3
Figure 2.8 Memory Data Formats
Data Format
7
7 6 5 4 3
MSB
MSB
MSB
0
2 1 0
LSB
LSB
LSB
21