RANA Systems Elite Controller, User Manual

Page: 291 / 328

ELITE SERIES USER MANUAL APPEN. A - DISK I/O
A minimum of five self-sync bytes must be main-
tained for each gap type, resulting in reason-
ably uniform gap sizes within each track.
A . 5 . 1 . G a p 1
This is the first data written to a track during
initialization. It originally comprises 128
bytes of self—sync, a large enough area to en-
sure that all parts of the track contain data.
Since the speed of a particular drive may vary,
the total length of the track in bytes is uncer—
tam and the percentage occupied by data is
unknown.
The initialization process is set up so that,
even on drives of differing speeds, the last
data field written will overlap Gap 1, provid-
ing continuity.
A . 5 . 2 . G a p 2
This appears after each Address field and before
each Data field, its length varying from five to
ten bytes on a normal drive. Gap 2 primarily
provides time for the data in an Address field
to be decoded before a read or write is ini—
tiated.
If the gap is too short, the start of the Data
field could spin past while DOS was still won-
dering if this was the sector to be read.
P a g e A - 2 0