2.3.2
Memory Data Formats
Figure 2.4 indicates the data formats in memory.
Word data stored in memory must always begin at an even address. In word access the least
significant bit of the address is regarded as 0. If an odd address is specified, no address error
occurs but the access is performed at the preceding even address. This rule affects MOV.W
instructions and branching instructions, and implies that only even addresses should be stored in
the vector table.
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
Note: * Ignored on return
Legend:
CCR: Condition code register
Figure 2.4 Memory Data Formats
When the stack is addressed by register R7, it must always be accessed a word at a time. 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.
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HITACHI [ HITACHI SEMICONDUCTOR ]
