Rainbow Electronics ATmega128L - Manual (Page 321)

321
ATmega128(L)
2467B–09/01
Figure 158. External Memory Timing (SRWn1 = 1, SRWn0 = 0)
Figure 159. External Memory Timing (SRWn1 = 1, SRWn0 = 1) (1)
Note: 1. The ALE pulse in the last period (T4-T7) is only present if the next instruction
accesses the RAM (internal or external).
ALE
T1 T2 T3
Write
Read
WR
T6
A15:8 Address Prev. addr.
DA7:0 Address Data Prev. data XX
RD
DA7:0 (XMBK = 0) Data Prev. data Address
System Clock (CLK CPU )
1
4
2
7
6
3a
3b
5
8 12
16
13
10
11
14
15
9
T4 T5
ALE
T1 T2 T3
Write
Read
WR
T7
A15:8 Address Prev. addr.
DA7:0 Address Data Prev. data XX
RD
DA7:0 (XMBK = 0) Data Prev. data Address
System Clock (CLK
CPU
)
1
4
2
7
6
3a
3b
5
8 12
16
13
10
11
14
15
9
T4 T5 T6