Bally 5000 Plus, Manual

Page: 318 / 388

1 2 . VACUUU FLUORESCENT D I SPLAY BOARD
C i r cu i t Descr i pt i on ( cont ' d )
R e f r es h / S e l ec t
The r e f r e s h / s e l ec t c i r cu i t a t U 1 3
and U 1 4 ( se r l a l / p a r a l l e i s h i f t
r eg i s t e r s ) con t i nuous l y r e f r es h e s
t he d a t a o f e a c h c ha r ac t e r o f U 1 8 .
The ch a r a c t e r s a r e r e f r e s h e d I n
pa i r s ( e . g . G20 on top a n d G20 on
bot t om ) .
U 1 7 p i n 26 con t i nuous l y sends a
s e r i a l b i t s t r eam ( H I GH e v e r y 2 0 t h
I nput ) t o U 1 4 p i n 1 4 . S i nce U 1 4
and U 1 3 a r e c a s c a de d , t h i s s e r i a l
b i t s t r e am ou t pu t s f r om U 1 4 p i n 1 6
t o U 1 3 p i n 1 4 .
The s e r i a l t o p a r a l l e i conve r s i on
o f U 1 3 a n d U 1 4 p ro v i de s a scann i ng
g r i d pu l se t o a p a i r o f c h a r a c t e r s .
The H I GH scann i ng g r i d pu l se b i a se s
t he g r i d pa i r . T h e 3 5 do t d a t a
s i gna l s I n t he pa i r a r e v a l i d .
Rese t
J 1 p i n 2 7 sends a l og i c
LOW
r e s e t t i ng U 1 7 a t p i n 6 a n d d i sa b l es
t h e ou t p u t s o f U 1 3 a n d U 1 4 a t p i n
1 3 .
T h i s R E S E T s i gn a l o r i g i na t e s
o n t he M P U boa r d a t U 1 9 p i n 7 . Th i s
I s no t a SYSR E S E T .
1 2- 1 0
R E F R E S H / S E L ECT D I AGRAM
U 1 8
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U 1 7
6 8 B 7 0 1 - M C U
F i g . 1 2- 5
J 1
21