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4.
READ, WRITE, AND BUS CONTROL
o
,
Q.V
-S
~~
'f
f:-E.R
S
?4L.S~~+
o'J u2
~fMirt ~
L---------u
o
1
TO
WR\TE EN~
wE*"
(p,~
\0)
( $
MJ...
~\\A.\'- (!,H-\P$
The write strobe to the 2114L chips. qnd the read/wrrte control s(gnals for
BUS BUFFER di recttonql control is, the implementati"on of the followi'ng Booleqn
Logic:
ROM;' ·
=:
[(SX
+
Sy) • MERQ
• READ]
WRM;'·::= [(SX
+
Sy) • MERo.
• WR ITE]
If Intel Mask ROM 3625 is to be used, It is necessary to cut the two traces
of the WRM* line and ground pin 10 of qllmemory sockets!
Pads qre provided
for this option.
(PROMs. and RAMs may not be mixed on the same card).
NOTE:
The Card's data bus drivers (74LS244) Ul and U2 are enabledanytlme
a valid address is present even
if
memory chips qre not plugged in.
The card
address range is chosen to prevent bus content ion wi'th other system memory
elements including processor on-card memory, other memory cards, and memory
mapped I/O.
7
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