AT90S4414/8515
83
External Clock Drive Waveforms
Figure 67. External Clock
Note:
See “External Data Memory Timing” on page 84. for a description of how the duty cycle influences the timing for the External
Data Memory
Figure 68. External RAM Timing
T3 is only present when wait-state is enabled.
Table 37. External Clock Drive
Symbol
Parameter
V
CC
= 2.7V to 4.0V
V
CC
= 4.0V to 6.0V
Units
Min
Max
Min
Max
1/t
CLCL
Oscillator Frequency
0
4
0
8
MHz
t
CLCL
Clock Period
250
125
ns
t
CHCX
High Time
100
50
ns
t
CLCX
Low Time
100
50
ns
t
CLCH
Rise Time
1.6
0.5
µs
t
CHCL
Fall Time
1.6
0.5
µs
VIL1
VIH1
System Clock O
ALE
WR
RD
Data / Address [7..0]
Data / Address [7..0]
Address [15..8]
Address
Address
Address
T1
T2
T3
T4
Prev. Address
Prev. Address
Prev. Address
1
0
4
2
13
3a
5
Note: Clock cycle T3 is only present when external SRAM waitstate is enabled
10
12
14
15
11
8
9
16
7
6
3b
Data
Data
Wr
ite
Read
Addr.
Addr.