R01UH0092EJ0110 Rev.1.10
Page 149 of 807
Jul 31, 2012
M16C/64C Group
11. Bus
11.3.5.8
External Bus Status When Internal Area is Accessed
Table 11.9 lists the External Bus Status When an Internal Area is Accessed. Figure 11.5 shows the
Typical Bus Timings When Accessing SFRs.
Figure 11.5
Typical Bus Timings When Accessing SFRs
Table 11.9
External Bus Status When an Internal Area is Accessed
Item
SFR Accessed
Internal ROM or RAM Accessed
A0 to A19
Address output
Retain the last accessed address of external area or SFR
D0 to
D15
Read
High-impedance
High-impedance
Write
Data output
Undefined
RD
,
WR
,
WRL
,
WRH
RD
,
WR
,
WRL
,
WRH
output
High-level output
BHE
BHE
output
Retain the last accessed status of external area or SFRs
CS0
to
CS3
High-level output
High-level output
ALE
Low-level output
Low-level output
WD
RD
A
A
Bus cycle = 2
φ
(1)
1 Wait State (1
φ
+ 1
φ
)
i = 0 to 3
A : Address RD : Read data WD : Write data
Bus cycle = 2
φ
(2)
2 Wait States (1
φ
+ 2
φ
)
WD
Bus cycle = 3
φ
Bus cycle = 3
φ
RD
BCLK
BCLK
CSi
RD
Data
Address
CSi
RD
Data
Address
High
High
A
A
WR
,
WRL
,
WRH
WR
,
WRL
,
WRH
Содержание M16C Series
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