4 .
I /O BOARD
C i r cu i t D e s c r i p t i on ( cont ' d )
Oecode O u t p u t Po r t
T h e de-mu l t i p l e x e r s
decode
t he ou t pu t
( F 2 a n d F 4 )
po r t s .
T h e
M P U boa r d t he n wr i t e s da t a b y t e s o r
wo r d s t o t h e ou t pu t po r t s .
Wr i t e l owe r d a t a b y t e s
T o de code t he o u t p u t por t s t o wr i t e
t o t h e l owe r da t a b y t e s ,
F 2
( 1 ) odd a d d r e s s s i g na l s f r om
( 2 )
decoded
odd
a d d r e s s
n e e d s
A 1 -A3
( 3 )
( 4 )
( 5
)
I /ODTACK s e n t t o t h e MPU boa r d
a c t i ve
LOW WR I T E s i gn a l
and
l owe r d a t a s t robe ( O SO ) s i gn a l .
An a c t i ve LOW WR I T E s i gna l ( P 1 p i n
1 4A ) ,
f r om
t h e MPU boa r d R/
W
s i g na I , goes
t o G 2 p i n 4 .
T h e
a c t i ve
LOW
( O SO ) s i gn a l
( P 1 p i n
1 3A ) ,
f r om
t he
MPU boa r d L O S
s i gna l , goes t o G 2 p i n
5 .
G 2 p i n 6
sends t he g a t e d s i gn a l s t o F 2 p i n
5
a s c h i p s e l e c t 3 ( CS 3 ) .
F 2 decodes
t he s e l e c t e d por t
and
sends a wr i t e pu l se ( WP ) s i gna l
t o
t h e
po r t .
T h e M P U boa r d t h en
wr i t e s
l owe r da t a b y t e s over
t h e
l owe r da t a l i ne s ( 00-07 ) .
Wr i t e uppe r da t a b y t e s
T o decode t he ou t pu t por t s t o wr i t e
needs
A 1 -A3
( 3 )
( 4 )
( 5 )
t o t h e uppe r d a t a b y t e s ,
F 4
( 1 ) even add r e s s s i gn a l s f r om
( 2 )
decoded even
a d d r e s s
I /OOTACK s e n t t o t h e MP U boa r d
a c t i ve
LOW
s i gn a l
and
uppe r da t a s t robe ( OS 1 ) s i g na l .
An
a c t i ve LOW WR I T E S i gn a l goes
�
G2
p i n 2 .
T h e a c t i v e
LOW O S 1
s i gna l
( P 1
----E
i n 1 2A ) ,
f r om
t h e
MPU boa r d U O S s i gn a l ,
goe s to
G 2
p i n 1 .
G2 p i n 3 s e n d s t h e
ga t ed
s i gna l t o F 4 p i n
5
a s c h i p s e l e c t 3
( CS 3 ) .
4-8
NOT E S
Summary of Contents for 5000 Plus
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Page 361: ...1 5 APPEND I CES APPEND I X 4 Co i n Mechan i sm I nc 1 5 6...
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