16-Bit, Three-State-Access Areas: Figures 6-6 to 6-8 show the timing of bus control signals for a
16-bit, three-state-access area. In these areas, the upper address bus (D
15
to D
8
) is used to access
even addresses and the lower address bus (D
7
to D
0
) is used to access odd addresses. Wait states
can be inserted.
Figure 6-6 Bus Control Signal Timing for 16-Bit, Three-State-Access Area (1)
(Byte Access to Even Address)
ø
Address bus
CS
AS
RD
D to D
D to D
HWR
LWR
D to D
D to D
n
15 8
7 0
15 8
7 0
T
1
T
2
T
3
Read
access
Write
access
Bus cycle
Even external address in area n
Valid
Invalid
Valid
Undetermined data
High
Note: n = 7 to 0
127
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