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CHAPTER 4 External Bus Interface
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Width of bus of 8 bits
Figure 4.6-7 External bus access on 8-bit bus width
LSBMSB
11
10
01
8bit
00
11
10
01
00
11
10
01
00
11
10
01
00
(a) PA1/PA0="00"
Output A1/A0="00"
Output A1/A0="01"
Output A1/A0="10"
Output A1/A0="11"
(b) PA1/PA0="01"
Output A1/A0="00"
Output A1/A0="01"
Output A1/A0="10"
Output A1/A0="11"
(c) PA1/PA0="10"
Output A1/A0="00"
Output A1/A0="01"
Output A1/A0="10"
Output A1/A0="11"
(d) PA1/PA0="11"
Output A1/A0="00"
Output A1/A0="01"
Output A1/A0="10"
Output A1/A0="11"
11
10
01
00
11
10
01
00
11
10
01
00
11
10
01
00
(a) PA1/PA0="00"
Output A1/A0="00"
Output A1/A0="01"
(b) PA1/PA0="01"
Output A1/A0="00"
Output A1/A0="01"
(c) PA1/PA0="10"
Output A1/A0="10"
Output A1/A0="11"
(d) PA1/PA0="11"
Output A1/A0="10"
Output A1/A0="11"
11
10
01
00
11
10
01
00
11
10
01
00
11
10
01
00
(a) PA1/PA0="00"
Output A1/A0="00"
(b) PA1/PA0="01"
Output A1/A0="01"
(c) PA1/PA0="10"
Output A1/A0="10"
(d) PA1/PA0="11"
Output A1/A0="11"
(A) Word access
(B) Halfword access
(C) Byte access