Spectravideo SVI 318 Service – Technical Manual page 93

th i s b i t spec i f i e s the numbe r o f �s top b i t s i n each t r a n sm i t t e d o r
B i t 2 :
r e c e i ve d s e r i a l cha r ac t e r .
che c k e d in t h e t r ansm i t o r re c e i v e da t a , re s p e c t i ve l y .
wh en a 5-b i t word l eng th i s s e l e c t e d v ia b i t s 0 and 1 , 1 - 1 / 2 S t op b i t s are
g e n e r a t e d o r check e d .
i s
l en g t h se l e c te d , 2 S t op b i t s a re g e ne r a t e d o r check e d .
B i t 3 : Th i s b i t i s the Par i t y Enab l e b i t .
b i t i s gene r a t e d ( t ra n sm i t d a t a ) o r checke d ( re c e i ve d a t a ) be tween the l a s t
dat a wo r d b i t and S t o p b i t o f t h e s e r ia l da t a .
p roduce an even o r o dd num b e r of l s when the d a t a word b i t s and the P a r i ty b i t
are s umm e d ) .
B i t 4 : Th i s b i t i s the Even P a r i t y S e l ec t b i t .
bit 4 is a log ic 0 , an odd numb e r of l og i c l s i s t ra n sm i t te d or checked in the
dat a wor d b i t s and P a r i t y b i t .
an even numb e r o f b i t s i s t ra n sm i t te d or check e d .
B i t 5 : Th i s b i t i s the S t i ck Par i t y b it .
a log ic 1 , t he P a r i t y b i t i s t ra n sm i t te d and t hen d e t e c t e d b y the rece i ve r a s a
l o g ic 0 i f b i t 4 i s a l o g i c 1 or a s a log i c 1 i f b i t 4 a l og i c 0 .
6 :
B i t T h i s b i t i s t he S e t Br eak C on t r o l b i t .
se r i a l o u t p u t ( SOUT ) is f o r c e d t o the Spac ing ( l o g i c 0) s t a t e and rema i n s t he re
reg a r d l e s s o f o t h e r t ra n sm i t t e r a c t i v i t y
b i t 6
to a l o g ic 0 .
comp u t e r commun i c a t i o n s s y s t e m .
B i t 7 : Th i s b i t i s t h e D iv i s o r L a t c h Acc� s s B i t ( DLAB ) .
( l og ic to acce s s t he D i v i sor L a t ch e s of the B a ud R a t e Gene r a t or du r ing a
1 )
Rea d or Wri t e ope ra t i o n .
Bu f f e r , t he T r a n sm i t t e r Ho l d ing Reg i s t e r , o r t he I nt e r r up t Enab l e Reg i s t e r .
INS8 2 50 P rogrammab le Baud Ra t e Gene r a t or
The INS8 2 50 co nta i n s a p ro g ramma b l e Baud Ra t e Gene r a t o r tha t i s capab l e o f
u
tak ing any c l ock i n p u t ( DC t o 3 . 1 MHz ) a n d d i v i d ing i t by any d i v i sor f rom 1 t o
1 6
( 2 1 ) . The o
[
d i v i s o r #
( f re quency input ) - ( baud r a t e x 1 6 ) ] .
=
the d i v i s o r in a 1 6-b i t b inary f o rma t .
du r ing i n i t i a l i z a t i on in order t o i nsure d e s i re d ope ra t i on o f t he Baud Rat e
Gene r a t o r . Upon l o a d i ng e i th e r o f the D iv i s o r L a t c he s , a 1 6-b i t Baud coun t e r
i s imme d ia t e l y l oade d .
I f b i t 2 i s
I f b i t 2 i s a l o g i c 1 whe n e i t he r a
Whe n b i t 3 is a l o g i c 1 and b i t 4 is a logic 1 ,
Th i s f e a t ure enab l e s the CPU to a l e r t a t e rm ina l in a
I t mus t be se t l ow ( l o g i c 0 ) t o acce s s the Rece ive r
t p u t f re quency of the Baud Gene ra t o r i s 1 6 x t h e Baud ra t e
Th i s p r e v i o u s s l ong counts on i n i t i a l l oa d .
4 . 60
·
a l o g i c 0 , 1 S t op b i t i s gene r a t e d o r
I f b i t 2 i s a l og i c 1
When b i t 3 i s a l o g i c 1 , a Par i t y
( T he P a r i t y b i t i s u s e d to
Whe n b i t 3 i s
Whe n b i t 3 i s a l o g i c 1 and b i t 5 i s
6
When b i t
T he s e t b re ak i s d i sab l e d b y s e t t ing
.
Two 8-b i t l a tches s tore
The s e D iv i so r La t c he s mus t be loaded
6 ,
7 , or 8-b i t wo r d
a
l o g i c 1 and
i s a log i c 1 , the
I t mu s t be s e t h igh