Teac FD-55 Series - 253

same recalibrate operation as after power-on in order to try to set to
the desired track again. If a desired sector cannot be found still
after several times of this series of operation, regard it as a hard
error Cunrecoverable errort.
If error occurs in read operation of data field, execute retry including
the recalibrate operation as' weIl as the above.
In read operation when the disk and the drive operate normally, it is
specified that the recoverable error (soft error) may occur less than
one per 10
9
bits. This error rate corresponds to one error per 24 hrs.,
approx. in continuous randum seek operation.
For the head seek operation, a method to unload the head before the
seek is often adopted. However, taking the disk damage caused by
repetitious impacts of head loading ttapping impact), access speed,
and tapping noise into consideration, it is desirable to perform the
seek operation with head load condition.
Tapping damage is negregible for a single sided FDO.
For a double sided FOO, it is specified that no error occurs by 3xl0
4
taps to a single point on a track. In practical operation, tappings
do not concentrate on a specific position, and lxl0
6
taps are allowable
on a track if they are distributed evenly on the track.
(Al Side selection
For a double sided FOO, it is required to designate a desired disk side
by the SICE ONE SELECT signal. 00 not change the level of the SIOE ONE
SELECT signal at least lmsec for FD-55A ~ Fand 590usec for FD-55G after
the change of the WRITE GATE signal to FALSE Ccompletion of write opera-
tion). The signal may be changed at any time except for the above
period.
Do not make the WRITE GATE signal TRUE at least lOO~sec after the change
of the SIDE ONE SELECT signal.
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