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6 multi-byte data in memory space, Multi-byte data in memory space, Accessing multi-byte data – FUJITSU F2MCTM-16LX User Manual

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CHAPTER 2 CPU

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 inputted 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.

Figure 2.6-1 Sample Allocation of Multi-byte Data in Memory

Accessing Multi-byte Data

Fundamentally, accesses are made within a bank. For an instruction accessing a multi-byte data item,

address FFFF

H

is followed by address 0000

H

of the same bank. Figure 2.6-2 is an example of an instruction

accessing multi-byte data.

Figure 2.6-2 Execution of MOVW A, 080FFFF

H

H

L

01010101

11001100

11111111

00010100

MSB

LSB

01010101

11001100

11111111 00010100

Address n

L

H

80FFFF

H

800000

H

01

H

23

H

??

??

23

H

01

H

AL before execution

AL after execution

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