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M 7.3500
Shown below is an enlarged view of data format
sequence. Writing Starts äs soon äs the Index hole comes
through the index detect hole.
1 Track
Sector 01
Sector 02
Final sector
/A
^
t
DATA
DATA
I ü
I I )
DA TA
INDEX
AM
Start point
Hatched portion is
a recording gap
I I )
AM
TT H H
SS
DL
CRC CRC
ID section CRC check code
Size of data section
(00) H-* 128bytes
(01) H -> 256 bytes
Sector number
Head number
(00) H - Head 0 (side 0)
(01) H -» Head 1 (side 1)
Track number
• l D address mark which
begins the ID section.
DATA
AM
>i
DATA
CRC CRC
Data
Data section
CRC check code
Data address mark
(or delete address mark)
NOTE: The delete address mark
is Written to indicate invalid
data. It is often Written on
a new floppy disk äs there are
no valid data on it.
7) Formatting
To write the above format (ID section, data section, gap)
on an entire surface of a new floppy disk is calied
formatting.
Note-1: Formatting may also be calied initialization. The
word "initialize" is also used äs a Software term to clear
the data section or to partition data area. Keep the
difference between formatting and initializing in mind.
Note-2: Unless formatting has been done on a properly
adjusted floppy disk drive unit, an erroe may occur on
another floppy disk drive unit.
8) Data write procedure
Described next is the procedure to write data on the FD.
(1) The head is moved over the track to be Written.
(2)
(3)
(4)
The head is loaded.
l D section is read and repeated until the desired
section is reached.
When the desired l D section is found, data is Written
on that area. (DATA AM is also Written.)
(5) The data thus Written is now checked if it was
Written correctly (read-after-write). The respective
l D section is read while the media makes a füll turn.
(6) The sector of the identical l D is read and verified
with the write data. Because of this read-after-write
capability the possibility of an error in the Written
data is quite Iow.
9) Data read procedure
Described next is the procedure to read data from the
FD.
(1) The head is moved over the track to lic read.
(2) The head is loaded.
(3) The ID section is read and repeated until the desired
sector is reached.
(4) When the identical IDsection is found, the data in
that data section is then read.
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