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IW4U!1j.ui\ly!n!!i'j!!
...
----.l_.~~
o
•
3.
CARD ADDRESS MAPPING
0000
3FFF
4000
7FFF
8000
BFFF
COOO
FFFF
o =
SX1~
(Lower 8K)
Sy~,:
(Upp'e r 8K)
16K BANKfl
=
SELECT
CARD SELECT
~
ADDRESS RANGE
'A'tsn4*
~
{
SO
0000"1 FFF
S 1
2000
-t
3FFF
o
0 0
001
{
S2
4000 +5FFF
S3
6000~7FFF
o
1 0
o
1 1
{
S4
8000 +9FFF -
sx~'~
S5
AOOO ."BFFF
--Sy~;~
1 0 0
1 0 1
{
S6
COOO -+DFFF
S 7
EOOO ..,. FFFF
1 1
0
1 1 1
CARD SELECT DECOD I NG 74LS42 (U4)
Lower 8K
Upper 8K
The upper three (A15, A14, A13) address lines are decoded by an 74LS42 (U4)
for card address selection.
A15 and A14 are decoded to select one of the
four 16 banks.
Address line A13 is decoded for selection of the lower 8K
(SX*) and the upper 8K (SV*) of the 16K bank.
14-1...S+~
I'IIt"'~~@-~
D
(IJ~)
II
0 -
16
}
C
(:,'<> '"
~.
f I"Ff
AI5
,~
c.
s"
@
S5
~'4.@-~-.
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&
~ ~
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~ f:~
t:
('S\\-ll'l'E~ POf:>I\loo-I~
S~
A
1
3@-
IS
A
.$2..
S J
~o
3
}
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J
o<::>~<:)..., ~\,<f'F
SY
*"
0PflE1< ~K ~t£eT\~
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