Spectravideo SVI 318 Service – Technical Manual page 92

Ou t p u t 1 ( OUT 1 ) , P i n 3 4 :
l o w p r o g r amm ing b i t 2 ( OUT 1 ) o f th e MODEM Con t r o l Reg i s t e r t o a h ig h leve l .
The O u t 1 s i g n a l i s s e t h i gh up on a M a s t e r R e s e t o p e r a t i on .
C h i p S e l e c t O u t ( C SOUT ) , P i n 2 4 :
se l e c t e d b y a c t i ve CSO , CS 1 , a n d C S 2 i n p u t s .
un t i l t h e CSOUT s i g na l is a l o g i c 1 .
D r i v e D i s a b l e ( DD I S ) , P i n 2 3 :
t he I N S 8 2 50 . A h i gh- l e ve l DDIS ou t pu t c an be u s e d to d i s ab l e an e x t e r na l
t r a n s c e i ve r ( i f u s e d be twe e n t h e CPU and I N S 8 2 50 on t h e D7 - D o
a l l t i m e s , e x c e p t when t he CPU i s r ea d ing da t a .
Baud O u t ( BAUDOUT ) , P in 1 5 :
t he I N S 8 2 50 . The c l ock ra t e i s e q u a l t o t he ma in re f e r e nce o s c i l l a to r
f re quency d i v i d e d
La t c h e s . T he BAUDOUT may a l s o be u s e d f o r t he r e c e iver s e c t i on b y t yp ing t h i s
ou t p u t t o t h e RCLK input o f t h e c h i p .
I n t e r r u p t ( I NTRP T ) , P i n 3 0 :
i n t e r r up t t yp e s ha s an a c t i ve h i gh cond i t i on and is enab l e d v i a t h e IER!
Re ce i v e r E r r or F l ag :
Empt y ; and MODEM S t a t us .
i n t e r r u p t s e r v i ce o r a Ma s t e r Re s e t ope r a t i on .
I N S 8 2 50 L i ne Con t ro l Reg i s t e r
The s y s t em p rogramme r sp e c i f i e s t h e fo rma t o f the a s y nc h ronous d a t a
c omm un i c a t i o ns exch ange v ia t he L i ne C on t r o l Reg i s t e r .
co nt ro l l i n g t h e f o rma t , t h e p ro g ramme r ma y re t r i e ve t h e con t e n t s o f the L ine
C o n t r o l Reg i s t er for i n s p ec t i on .
and e l i m ina t e s t h e ne e d f o r s e p a r a t e s t o r a g e in s y s t em memo r y o f the l i
cha r a c t e r i s t i cs .
t a b l e 2 and a r e descr i b e d be l ow .
B i t s 0 and The s e t wo b i t s spe c i f y the numb e r o f b i t s i n e a c h t ransm i t t e d or
1 :
rece i ve d s e r i a l char a c t e r .
B i t
1
0
0
1
1
U s e r- d e s i g ne d o u t p u t t h a t can be s e t t o an act ive
Whe n h i gh , in d i c a t e s t h a t t h e c h ip h a s b e e n
Goe s low whe ne v e r the CPU i s r e a d ing d a t a f rom
1 6 x c l oc k s i gna l for the t ra n sm i t t e r sec t i o n o f
t h e s pe c i f i e d d i v i s o r i n t h e Baud Gene ra t o r D iv i s o r
G o e s h i gh whe never any one o f t h e f o l l ow ing
R e c e i v e r Data Ava i l ab l e :
The INTRPT s i gna l i s re s e t l ow upon t h e app rop r i a t e
T h i s f e a t u re s i mp l i f i e s s y s t em p ro g r amm ing
T he c o n t e n t s of t he L i ne Con t ro l Reg i s t e r a re i n d i c a t e d i n
The enco d in g of b i t s 0 and 1 is f o l l ows :
B i t 0
0
1
0
1
4 . 59
N o d a t a t r a ns f e r c an b e i n i t i a t ed
T r a n sm i t t e r H o l d ing Reg i s t e r
I n a d d i t i on t o
Wo r d Leng t h
5 B i t s
6 B i t s
7 B i t s
8 B i t s
Da t a Bus ) a t