2.3.2
Memory Data Formats
Figure 2-4 indicates the data formats in memory. The H8/300L CPU can access word data stored
in memory (MOV.W instruction), but the word data must always begin at an even address. If word
data starting at an odd address is accessed, the least significant bit of the address is regarded as 0,
and the word data starting at the preceding address is accessed. The same applies to instruction
codes.
Data Type
Address
Data Format
7
0
1-bit data
Byte data
Address n
Address n
7
6
5
4
3
2
1
0
MSB
MSB
LSB
Upper 8 bits
Lower 8 bits
Even address
Odd address
Word data
Byte data (CCR) on stack
Word data on stack
LSB
MSB
MSB
CCR
LSB
LSB
Even address
Odd address
CCR*
MSB
Even address
Odd address
LSB
CCR: Condition code register
Note: * Ignored on return
Figure 2-4 Memory Data Formats
When the stack is accessed using R7 as an address register, word access should always be
performed. When the CCR is pushed on the stack, two identical copies of the CCR are pushed to
make a complete word. When they are restored, the lower byte is ignored.
21
ETC [ ETC ]
