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9.4 Microcontroller Interface Timings
9.4.1 External Memory Interface
Figure 9.5
External Memory Interface Waveforms
t
1
ALE
PSEN/
ADDR
t
6
AD[7:0]
ADDR
A[15:8]
ADDR
A[7:0]
Table 9.14
External Memory Interface Timings
Symbol
Parameter
T
ALE pulse width = duration of positive ALE pulse
1
T
PSEN/ pulse width = duration of negative PSEN/ pulse
2
T
PSEN/ falling to instruction valid = maximum delay from
3
PSEN/ falling to input data valid
T
Data hold to PSEN/ rising = minimum hold time for data
4
after PSEN/ rises
T
ALE falling to instruction valid = maximum delay from ALE
5
falling to input data valid
T
Address valid to ALE falling = minimum setup time for
6
A[15:8] and AD[7:0] to ALE falling
This section provides timing information for the microcontroller interface.
The AC characteristics described in this section apply over the entire
range of operating conditions for the SYM53C040.
t
2
t
3
INSTR
t
5
ADDR
ADDR
Microcontroller Interface Timings
t
4
ADDR
INSTR
Min
Max
Units
23
–
ns
75
–
ns
–
55
ns
0
–
ns
–
80
ns
20
–
ns
9-9
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