131
ATmega161(L)
1228B–09/01
External Data Memory Timing
Notes:
1. This assumes 50% clock duty cycle. The half period is actually the high time of the external clock, XTAL1.
2. This assumes 50% clock duty cycle. The half period is actually the low time of the external clock, XTAL1.
Table 51.
External Data Memory Characteristics, 4.0 - 5.5 Volts, No Wait State
Symbol
Parameter
8 MHz Oscillator
Variable Oscillator
Unit
Min
Max
Min
Max
0
1/t
CLCL
Oscillator Frequency
0.0
8.0
MHz
1
t
LHLL
ALE Pulse Width
95
1.0t
CLCL
-30
ns
2
t
AVLL
Address Valid A to ALE Low
22.5
0.5t
CLCL
-40
ns
3a
t
LLAX_ST
Address Hold After ALE Low,
write access
10
10
ns
3b
t
LLAX_LD
Address Hold after ALE Low,
read access
15
15
ns
4
t
AVLLC
Address Valid C to ALE Low
22.5
0.5t
CLCL
-40
ns
5
t
AVRL
Address Valid to RD Low
95
1.0t
CLCL
-30
ns
6
t
AVWL
Address Valid to WR Low
95
1.0t
CLCL
-30
ns
7
t
LLWL
ALE Low to WR Low
42.5
145
0.5t
CLCL
-20
0.5t
CLCL
+20
ns
8
t
LLRL
ALE Low to RD Low
42.5
145
0.5t
CLCL
-20
0.5t
CLCL
+20
ns
9
t
DVRH
Data Setup to RD High
60
60
ns
10
t
RLDV
Read Low to Data Valid
65
65
ns
11
t
RHDX
Data Hold After RD High
0
0
ns
12
t
RLRH
RD Pulse Width
105
1.0t
CLCL
-20
ns
13
t
DVWL
Data Setup to WR Low
27.5
0.5t
CLCL
-35
ns
14
t
WHDX
Data Hold After WR High
27.5
0.5t
CLCL
-35
ns
15
t
DVWH
Data Valid to WR High
95
1.0t
CLCL
-30
ns
16
t
WLWH
WR Pulse Width
105
1.0t
CLCL
-20
ns
Table 52.
External Data Memory Characteristics, 4.0 - 5.5 Volts, 1 Cycle Wait State
Symbol
Parameter
8 MHz Oscillator
Variable Oscillator
Unit
Min
Max
Min
Max
0
1/t
CLCL
Oscillator Frequency
0.0
8.0
MHz
10
t
RLDV
Read Low to Data Valid
185
2.0t
CLCL
-65
ns
12
t
RLRH
RD Pulse Width
230
2.0t
CLCL
-20
ns
15
t
DVWH
Data Valid to WR High
220
2.0t
CLCL
-30
ns
16
t
WLWH
WR Pulse Width
230
2.0t
CLCL
-20
ns