117
ATmega103(L)
0945G–09/01
Figure 79.
External RAM Timing
External Clock Drive
Waveforms
Figure 80.
External Clock Drive Waveforms
Note:
See “External Data Memory Timing” on page 115. for a description of how the duty cycle
influences the timing for the external data memory.
System Clock Ø
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 Wait State is enabled.
10
12
14
15
11
8
9
16
7
6
3b
Data
Data
Wr
ite
Read
Addr.
Addr.
Table 49.
External Clock Drive
Symbol
Parameter
V
CC
= 2.7V to 3.6V
V
CC
= 4.0V to 5.5V
Units
1/t
CLCL
Oscillator Frequency
0.0
4.0
0.0
6.0
MHz
t
CLCL
Clock Period
250.0
167.0
ns
t
CHCX
High Time
100.0
67.0
ns
t
CLCX
Low Time
100.0
67.0
ns
t
CLCH
Rise Time
1.6
0.5
µs
t
CHCL
Fall Time
1.6
0.5
µs
VIL1
VIH1