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MB90335 Series
2.5
Multibyte Data in Memory Space
Multibyte data is allocated from the low-order addresses to the high-order addresses in
the memory space in the order from the byte in LSB to the byte in MSB.
■ Multibyte Data Allocation in Memory Space
Data is written to memory from the low-order addresses. Therefore, for a 32-bit data item, the lower 16 bits
are transferred before the upper 16 bits.
If a reset signal is input immediately after the lower bits are written, the upper bits might not be written.
Figure 2.5-1 shows a sample allocation of multibyte data in memory. The lower 8 bits of a data item are
stored at address n, then address n+1, address n+2, address n+3, etc.
"H"
01010101
11001100
11111111
00010100
n
location
"L"
■ Accessing Multibyte Data
Basically, all accesses are made within a bank. For an instruction accessing a multibyte data item, the next
address of FFFF
instruction accessing multibyte data.
80FFFF
H
800000
H
CM44-10137-6E
Figure 2.5-1 Sample Allocation of Multibyte Data in Memory
B
B
B
B
location is 0000
H
Figure 2.5-2 Execution of MOVW A, FFFFH
"H"
01
H
·
·
·
23
H
"L"
FUJITSU MICROELECTRONICS LIMITED
MSB
01010101
11001100
B
location of the same bank. Figure 2.5-2 shows an example of an
H
AL before execution
AL after execution
CHAPTER 2 CPU
2.5 Multibyte Data in Memory Space
11111111
00010100
B
B
??
??
23
01
H
H
LSB
B
27
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