Datasheet

32.9. External Data Memory Timing
Table 32-11 External Data Memory Characteristics, 4.5V - 5.5V, No Wait-state
Symbol Parameter 8MHz Oscillator Variable Oscillator Unit
Min Max Min Max
0 1/t
CLCL
Oscillator Frequency 0.0 16 MHz
1 t
LHLL
ALE Pulse Width 115 1.0t
CLCL
-10 ns
2 t
AVLL
Address Valid A to ALE Low 57.5 0.5t
CLCL
-5
(1)
ns
3a t
LLAX_ST
Address Hold After ALE Low,
write access
5 5 ns
3b t
LLAX_LD
Address Hold after ALE Low,
read access
5 5 ns
4 t
AVLLC
Address Valid C to ALE Low 57.5 0.5t
CLCL
-5
(1)
ns
5 t
AVRL
Address Valid to RD Low 115 1.0t
CLCL
-10 ns
6 t
AVWL
Address Valid to WR Low 115 1.0t
CLCL
-10 ns
7 t
LLWL
ALE Low to WR Low 47.5 67.5 0.5t
CLCL
-15
(2)
0.5t
CLCL
+5
(2)
ns
8 t
LLRL
ALE Low to RD Low 47.5 67.5 0.5t
CLCL
-15
(2)
0.5t
CLCL
+5
(2)
ns
9 t
DVRH
Data Setup to RD High 40 40 ns
10 t
RLDV
Read Low to Data Valid 75 1.0t
CLCL
-50 ns
11 t
RHDX
Data Hold After RD High 0 0 ns
12 t
RLRH
RD Pulse Width 115 1.0t
CLCL
-10 ns
13 t
DVWL
Data Setup to WR Low 42.5 0.5t
CLCL
-20
(1)
ns
14 t
WHDX
Data Hold After WR High 115 1.0t
CLCL
-10 ns
15 t
DVWH
Data Valid to WR High 125 1.0t
CLCL
ns
16 t
WLWH
WR Pulse Width 115 1.0t
CLCL
-10 ns
Note:
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 32-12 External Data Memory Characteristics, 4.5V - 5.5V, 1 Cycle Wait-state
Symbol Parameter 8MHz Oscillator Variable Oscillator Unit
Min Max Min Max
0 1/t
CLCL
Oscillator Frequency 0.0 16 MHz
10 t
RLDV
Read Low to Data Valid 200 2.0t
CLCL
-50 ns
12 t
RLRH
RD Pulse Width 240 2.0t
CLCL
-10 ns
Atmel ATmega64A [DATASHEET]
Atmel-8160E-ATmega64A_Datasheet_Complete-09/2015
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