Multi-Byte Data In Memory Space - Fujitsu MB90390 Series Hardware Manual

2.6

Multi-byte Data in Memory Space

Data is written to memory from the low-order addresses. Therefore, for a 32-bit data
item, the low-order 16 bits are transferred before the high-order 16 bits.
If a reset signal is input immediately after the low-order bits are written, the high-order
bits might not be written.
■ Multi-byte Data Allocation in Memory Space
Figure 2.6-1 is a diagram of multi-byte data configuration in memory. The low-order eight 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
Address n
"L"
■ Accessing Multi-byte Data
Fundamentally, accesses are made within a bank. For an instruction accessing a multi-byte data item,
address "FFFF
MOVW A, 080FFFFH.
80FFFF H
800000 H
Figure 2.6-1 Sample Allocation of Multi-byte Data in Memory
" is followed by address "0000
H
Figure 2.6-2 Execution of MOVW A, 080FFFFH
"H"
01 H
·
·
·
23 H
"L"
MSB
11001100
01010101
B
B
" of the same bank. Figure 2.6-2 shows an execution of
H
AL before execution
AL after execution
CHAPTER 2 CPU
LSB
11111111 00010100
B B
?? ??
23 H 01 H
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