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Memory Data Structure: Figure 1-2 indicates the data structure 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
1-Bit data
Byte data
Word data
Byte data (CCR) on stack
Word data on stack
CCR: Condition code register.
Note: Word data must begin at an even address.
:
Ignored when return.
*
The stack is always 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 returned, the
lower byte is ignored.
1.1.3 Address Space
The H8/300 CPU supports a 64K-byte address space. The memory map differs depending on
the particular chip in the H8/300 Series and its operating mode. See the Hardware Manual of
the chip for details.
Address
Address n
Address n
Even address
Odd address
Even address
Odd address
Even address
Odd address
Figure 1-2. Memory Data Formats
4
Data format
7
0
7 6 5 4 3 2 1 0
M
L
S
S
B
B
M
Upper 8 bits
S
B
L
Lower 8 bits
S
B
M
L
CCR
S
S
B
B
M
L
*
CCR
S
S
B
B
M
Upper 8 bits
S
B
L
Lower 8 bits
S
B
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