Table of Contents
Advertisement
S e c t o r F o r m a t
The n u m b e r o f s e c t o r s In e a c h t r a c k Is d e t e r m i n e d by the a p p l i c a t i o n , and can
r a n g e f r o m 1 to 3 2 , d e p en d in g on w h e t h e r the s o f t - s e c t o r o r h a r d - s e c t o r f lo p p y
d i s k is b e i n g u sed .
When s o f t s e c t o r o p e r a t i o n is r e q u i r e d , o n l y on e index hole is punched in the flo pp y
d is k .
With this d i s k , the c o n t r o l l e r u s e s the index p u l s e to d e f in e the s e c t o r s .
When hard s e c t o r o p e r a t i o n is r e q u i r e d , the fl o p p y d i s k u s e d c o n t a i n s the index
h ole plus 32 s e c t o r h o l e s s p a c e d e q u i d i s t a n t ar ou nd the d i s k ( s e e F i g u r e 1-2).
T h e in d ex hole is punched m i d w a y b e t w e e n s e c t o r h o l e s 31 and 0.
p u l s e o f s e c t o r 31 and in d ex a l e r t s the c o n t r o l l e r that th e nex t p u l s e s t a r t s s e c t o r 0.
Th e in d ex and s e c t o r h o l e s a r e s e n s e d p h o t o e l e c t r i c a l l y , p r o v i d i n g the p u l s e s s u p
p li e d to the c o n t r o l l e r .
S e c t o r Content
T h e f o r m a t o f e a c h s e c t o r is d e t e r m i n e d by the a p p li c a t i o n .
and p o s t a m b l e s co n t ai n in g a s t r e a m of co d ed b y t e s a r e w r i t t e n at the b e g in n in g and
end o f e a c h s e c t o r , to p r o v i d e data s y n c h r o n i z a t i o n .
e a c h n e w t r a c k , an id e n t i f i c a t i o n (ID) f i e l d is w r i t t e n c o n t a in in g the t r a c k and s e c t o r
n u m b e r s .
F o l l o w i n g the ID f i e l d , data b y t e s a r e w r it t e n .
3 2 - S e c t o r F o r m a t
T h i s f o r m a t is not the m o s t e f f i c i e n t OEM f o r m a t due to the n u m b e r of gaps
r e q u i r e d b e t w e e n data r e c o r d s .
but is a c c e p t e d a s the m o s t c o m p a t i b l e .
F i g u r e 1-4.
SECTOR
PREAMBLE
T h e IBM 3740 f o r m a t r e q u i r e s e v e n m o r e gaps
A t y p i c a l 3 2 - s e c t o r f o r m a t is s h o w n in
DATA RECORD
F i g u r e 1- 4 .
3 2 - S e c t o r F o r m a t
1 - 6
T h e d o u b l e -
N o r m a l l y , p r e a m b l e s
F o l l o w i n g the p r e a m b l e o f
SECTOR
POSTAMBLE
Advertisement
Table of Contents
