Spectravideo SVI 318 Service – Technical Manual page 94

Tab l es 3 and i l l us t rate the use of
4
f re quencies of
1 . 8432 MHz
and be low the e r ror ob ta ined i s minima l .
is de pendent on t he crys t a l f requency chosen .
Not e : The max imum operat ing f re quency
Howeve r , when us ing divisors of
is e qual to the divi sor in
then t he ma ximum f requency i s
rate be greater than 56K Baud .
Line S ta tus Reg i s t e r
This 8-b i t reg i s t e r provides stat us informa t ion to the CPU conce rning the data
t ransfe r . The contents of the L i ne S tat us Reg i s t e r are ind icated in tab le
and are descr ibed be l ow .
0 :
B i t Th is b i t is the receer Dat a Ready ( DR ) ind icator .
log ic 1 wheneve r a comp le te incoming cha rac t er has been rece ived and t rans­
f e r r e d into the Receive r Buf fer Reg i s te r .
e i th e r by t he CPU reading the da t� in t he Rece iver Buffer Reg i s ter or by
wr i t ing a log ic
0
B i t 1 : This b i t is the Ove rrun E r ror { OE ) ind icat o r .
dat a in th e Rece i ver Buf fer Reg i s t e r was no t r ea d b y the CPU be fore the nex t
char a c t e r was t rans f e r re d into t he Rece iver Bu f f er Reg i s te r , t he reby des t roying
the p revious cha racte r .
conten t s of t he L i ne S t atus Reg i s t e r .
Bi t 2 : Thi s b i t is the Par i t y Error ( PE ) indicat or .
rece i ved da ta cha racter does not have t he correct even or odd par i t y , as
se l e c t e d by the even-pa ri t y-se l ec t b i t .
de te c t i on of a par ity e rror and is reset to a log ic
the cont ents of the L ine S ta tus Registe r .
and
3 . 0 7 2 MHz
MHz .
into it f rom the CPU .
The OE indi ca tor is re set wheneve r the CPU read s the
4
die BS'ud
Rat e Gener tor with crysta l
respect ive ly . For baud rates of
The accuracy of the des i re d baud rate
of the Baud Gene rator is
and be low , the maximum f requency
3
For examp l e , if the divisor is
In no case shou ld the data
MHz .
1
B i t may be re set t o a log ic
0
B i t
B i t
The PE b i t is set to a log ic
whenever the CPU reads
0
61
•.
38400
3 . 1 MHz .
1 ,
2
B i t i s s e t t o a
0
0
indicates t ha t
1
2 ind icates tha t the
upon
1