Fujitsu FR20 ユーザーズマニュアル

4.6.2

Bus Access of Big Endian

The data format in the FR20 series is normally big endian. Thus, external bus access is
big endian for areas in which little endian (LER) is not set.

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Data Format

The relationship between the internal register and external data bus is indicated per data format.

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Half-word access (LDUH, STH instruction execution)

Figure 4.6-2 Relationship between the internal register and external data bus of half-word access

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Byte access (LDUH, STH instruction execution)

Figure 4.6-3 Relationship between internal register and external data bus of byte access

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Data Bus Width

The relationship between the internal register and external data bus is indicated per data bus width.

b) Output address Lower"10"

D31

D15

D23

Internal register

D31

D15

D23

External bus

a) Output address Lower"00"

D31

D15

D23

Internal register

D31

D15

D23

External bus

D31

D15

D23

Internal register

D31

D15

D23

External bus

Internal register

External bus Internal register

External bus

a) Output address Lower"00"

D31

D15

D23

D31

D15

D23

b) Output address Lower"01"

D31

D15

D23

D31

D15

D23

c) Output address Lower"10"

D31

D15

D23

D31

D15

D23

d) Output address Lower"11"