Rainbow-electronics ATmega161L Manuel d'utilisateur télécharger pdf (Page 86)

ATmega161(L)

1228C–AVR–08/02

Figure 49. External Memory with Page Select

Figure 50. External Data Memory Cycles without Wait State (SRWn1 = 0 and SRWn0

=0)

(1)

Note: 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).

$0000

Data Memory

$0460

External Memory

(0-63K x 8)

$FFFF

Internal memory

SRL[2..0]

SRW11

SRW10

SRW01

SRW00

Lower page

Upper page

System Clock Ø

ALE

Data/Address [7..0]

Address [15..8]

Address

T1 T2 T3

Data

Write

Read

Prev. addr.

Prev. data

1 2 ... 81 82 83 84 85 86 87 88 89 90 91 ... 158 159

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Rainbow-electronics ATmega161L Manuel d'utilisateur Page 86