Data Register; Track Register - Spectravideo SVI 318 Service – Technical Manual

FD1 793 FLOPPY DISK CONTROLLER DESCRIPTION
The F lo p p y D i sk Forma t t e r b l ock d i a g ram
i n c l ud e t he pa ra l l e l p r o c e s s o r i n t e r f a ce and t h e F l o p py D i sk i n t e r f ace .
FT
DATA S I REGISTER - Th i s 8-b i t r e g i s t e r a s s emb l es se r i a l data f rom
H
t h e Rea d Da t a i n pu t ( RAW READ ) du r i ng Re a d ope ra t i on s and t r ans f e r s s e r i a l data
to t he W r i te D a t a ou t p u t du r ing W r i te ope ra t i ons .

DATA REGISTER

- Th i s 8-b i t re g i s t e r i s us e d as a ho l d ing re g i s t e r du r ing D i s k
R e a d a n d Wri t e op e r a t i o n s .
t r a n s f e r r e d i n p a r a l l e l to t h e Da t a Reg i s t e r f rom t h e D a t a Sh i f t R e g i s t e r .
D i s k Wr i t e o p e r a t i o n s i n f o rma t i on i s t r a n s f e rre d in p a r a l l e l f rom the D a t a
Reg i s t e r to t h e Da t a Sh i f t Reg i s t e r .
Whe n e x e c u t i ng the S e e k command the Da t a Reg i s t e r ho l d s the a d d re s s o f t he
de s i re d T r ac k p o s i t i on .
t h e DAL un d er p roce s s o r c o n t ro l .

TRACK REGISTER

-
Rea d /Wr i t e h ea d pos i t i on .
s t ep p e d i n ( t owa r d s t r a ck 7 6 ) a n d decreme n t e d b y one when t h e head i s s t e p p e d
o u t ( t owards t r ack
re c o r d e d t r ack numb e r in t h e ID f i e l d du r i ng d i s k Rea d , Wr i t e , and Ve r i f y
o pe r a t i o ns . The Tr ack R eg i s t e r c an be l oa d e d f rom or t r ans f e r re d to the DAL .
Th i s Reg i s t e r shou l d no t b e l o a d e d whe n the dev i ce i s bus y .
SECTOR REGISTER ( SR)
se c t o r p o s i t i on .
s e c t o r numb e r in t he ID f i e l d du r ing d i sk R e a d o r Wr i t e ope r a t i ons .
Reg i s t e r co n t e n t s can be l o a de d f rom or t ra n s f e r re d t o the DAL .
s h ou l d n o t b e l oa d e d wh en t he devi ce is b us y .
COMMAN D REGISTER ( CR)
e x e c u t e d . T h i s reg i s t e r shou l d not be l oa d e d when t he d e v ice i s b us y un l e s s
t h e new conna nd i s a force i n t e r r up t .
t he DAL , b u t not rea d on t o t he
STATUS REGISTER ( STR)
The mean ing o f t he S t a t us b i t s i s a func t i on o f t he t ype o f c ommand p r e vi o u s ly
exec u t e d . Th i s reg i s t e r can be re a d on t o the DAL , but not l o a d e d f rom the
CRC LOGIC
- T h i s log ic i s u se d to check or to gene ra te the 1 6 -b it Cyc l ic
Re dundancy Check ( CRC ) .
I n D i s k Rea d op e ra t i on s the a s s emb l e d d a t a by t e i s
T h i s reg i s t e r i s l oa d e d f rom the DAL and ga ted� o n t o
Th i s 8-b i t reg i s t e r ho l d s the t rack numb e r o f the c u r rent
It i s i n c reme n t e d by one e very t i me t he head i s
T h e c on t e n t s of t he re g i s t e r a re com p a re d w i th the
00 ) .
T h i s 8-b i t reg i s t e r h o l d s t he a dd r e s s o f the d e s i re d
-
The co n t e n t s o f the re g i s t e r are compa r e d w i t h the rec o r d e d
Th i s 8 -b i t reg i s t e r ho l d s the command p re s en t l y be i ng
-
DAL .
Th i s 8-b i t reg i s t e r ho l d s dev i c e S t a t u s informa t i on .
-
the p o lynom ia l i s :
=
G ( x )
4 . 81
( STM-00 3 - C ) .
The command re g i s t e r can b e l oa d e d f rom
+ + +
x 12
x 1 6
x 5
The p r i ma r y s ec t i on s
Th i s re g i s t e r
1
I n
The S e c tor
DAL .