AT90S4414/8515
84
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 38. External Data Memory Characteristics, 4.0 - 6.0 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
32.5
0.5t
CLCL
-30.0
(1)
ns
2
t
AVLL
Address Valid A to ALE Low
22.5
0.5t
CLCL
-40.0
(1)
ns
3a
t
LLAX_ST
Address Hold After ALE Low,
ST/STD/STS Instructions
67.5
0.5t
CLCL
+5.0
(2)
ns
3b
t
LLAX_LD
Address Hold after ALE Low,
LD/LDD/LDS Instructions
15.0
15.0
ns
4
t
AVLLC
Address Valid C to ALE Low
22.5
0.5t
CLCL
-40.0
(1)
ns
5
t
AVRL
Address Valid to RD Low
95.0
1.0t
CLCL
-30.0
ns
6
t
AVWL
Address Valid to WR Low
157.5
1.5t
CLCL
-30.0
(1)
ns
7
t
LLWL
ALE Low to WR Low
105.0
145
1.0t
CLCL
-20.0
1.0t
CLCL
+20.0
ns
8
t
LLRL
ALE Low to RD Low
42.5
82.5
0.5t
CLCL
-20.0
(2)
0.5t
CLCL
+20.0
(2)
ns
9
t
DVRH
Data Setup to RD High
60.0
60.0
ns
10
t
RLDV
Read Low to Data Valid
70.0
1.0t
CLCL
-55.0
ns
11
t
RHDX
Data Hold After RD High
0.0
0.0
ns
12
t
RLRH
RD Pulse Width
105.0
1.0t
CLCL
-20.0
ns
13
t
DVWL
Data Setup to WR Low
27.5
0.5t
CLCL
-35.0
(2)
ns
14
t
WHDX
Data Hold After WR High
0.0
0.0
ns
15
t
DVWH
Data Valid to WR High
95.0
1.0t
CLCL
-30.0
ns
16
t
WLWH
WR Pulse Width
42.5
0.5t
CLCL
-20.0
(1)
ns
Table 39. External Data Memory Characteristics, 4.0 - 6.0 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
195.0
2.0t
CLCL
-55.0
ns
12
t
RLRH
RD Pulse Width
230.0
2.0t
CLCL
-20.0
ns
15
t
DVWH
Data Valid to WR High
220.0
2.0t
CLCL
-30.0
ns
16
t
WLWH
WR Pulse Width
167.5
1.5t
CLCL
-20.0
(2)
ns