atmega161-4pi ATMEL Corporation, atmega161-4pi Datasheet - Page 137

• Manufacturer Part Number: atmega161-4pi
• Description: 8-bit Microcontroller With 16k Bytes Of In-system Programmable Flash
• Manufacturer: ATMEL Corporation

1228D–AVR–02/07
Figure 85. External Memory Timing (SRWn1 = 1, SRWn0 = 0)
Figure 86. External Memory Timing (SRWn1 = 1, SRWn0 = 1)
Note:
Data/Address [7..0]
Data/Address [7..0]
Data/Address [7..0]
Data/Address [7..0]
System Clock Ø
System Clock Ø
Address [15..8]
Address [15..8]
1. The ALE pulse in the last period (T4 - T7) is only present if the next instruction
ALE
WR
RD
ALE
WR
RD
accesses the RAM (internal or external). The data and address will only change in T4
- T7 if ALE is present (the next instruction accesses the RAM).
Prev. data
Prev. data
Prev. addr.
Prev. data
Prev. data
Prev. addr.
T1
T1
XX
XX
XX
XX
XX
XX
1
Address
Address
4
2
1
T2
6
Address
5
Address
4
2
3a
3b
7
8
T2
6
5
13
3a
3b
10
7
8
Address
Data
13
Data
T3
10
Address
Data
Data
T3
16
12
T4
15
9
15
16
12
T4
9
T5
ATmega161(L)
(1)
11
T5
T6
14
11
14
T6
T7
XX
XX
XX
XX
XX
XX
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