Fujitsu mb91192 User Manual

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CHAPTER 4 External Bus Interface

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16-bit bus width

Figure 4.6-4 Relationship between internal register and external data bus of 16-bit bus width

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8-bit bus width

Figure 4.6-5 Relationship between internal register and external data bus of 8-bit bus width

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External Bus Access

External bus access (16-bit/8-bit bus width) is shown per word, half-word, and byte access in Figure 4.6-6

and Figure 4.6-7 . The following items are also shown in Figure 4.6-6 and Figure 4.6-7 .

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Access byte position

•

Program address and output address

•

Bus access count

The MB91191/MB91192 series do not detect the misalignment.

According to the word access, even if the address lower 2-bit specified by the program is "00", "01", "10",

or "11", the address lower 2-bit to be output will be all "00". In case of half-word access, when the lower

address is "00" or "01", "00" will be set, and when it is "10" or "11", "10" will be set.

D07

D15

D23

D31

D23

D31

"00"

External bus

Output addres lower

Internal register

"10"

read/write

External bus

Output addres lower

Internal register

D07

D15

D23

D31

"00"

D31

"01"

"11"

"10"

read/write

PA1/PA0

Output A1/A0

: Specified address lower 2-bit by program

: Output address lower 2-bit

: Output address start byte position

: Access data byte position

: Bus access count