atmega161-4pi ATMEL Corporation, atmega161-4pi Datasheet - Page 86

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

86
ATmega161(L)
Figure 49. External Memory with Page Select
Figure 50. External Data Memory Cycles without Wait State (SRWn1 = 0 and SRWn0
=0)
Note:
Data/Address [7..0]
Data/Address [7..0]
(1)
System Clock Ø
Address [15..8]
1. SRWn1 = SRW11 (upper page) or SRW01 (lower page), SRWn0 = SRW10 (upper
page) or SRW00 (lower page).
The ALE pulse in period T4 is only present if the next instruction accesses the RAM
(internal or external). The Data and Address will only change in T4 if ALE is present
(the next instruction accesses the RAM).
ALE
WR
RD
Prev. addr.
Prev. data
Prev. data
External Memory
(0-63K x 8)
T1
XX
XX
XX
Address
Address
Internal memory
Data Memory
Lower page
Upper page
SRW01
SRW00
SRW11
SRW10
T2
XX
Address
Data
Data
$0000
$0460
$FFFF
SRL[2..0]
T3
T4
1228D–AVR–02/07
XX
XX
XX