Mitsubishi Electric M4853, Руководство по обслуживанию

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8.3 Error Detection and Correction
8.3.1 Write Errors
If an error occurs during a write operation, it can be
detected by performing a read operation on the diskette
immediately following the write operation. This is
generally called a write check, which is an effective
means of p reventing write errors. It is recommended,
therefore, that a write check be made without fail.
If a write error occurs, repeat the write operation and
conduct a write check. If data cannot be c o r r e c t l y
written even after the write operation is repeated
about ten times, perform a read operation on another
track to d e t e r m i n e w h e t h e r the d a t a can be read
correctly. If so, a specific track of the diskette is
defective. If data cannot be c o rrectly read on the
other track, the drive is assumed to have some trouble.
If the diskette is defective, replace it.
8.3.2 Most data errors that occur are soft errors. If a read
error occurs, repeat the read operation to recover the
data.
The following are possible main causes of soft errors:
o Dust is caught between the read/write head and
diskette causing temporary fault in head contact.
Such dust is g e n e r a l l y removed by the s e l f ­
cleaning wiper of the jacket, and the data is
recovered by the next re-read operation. If
read/write is continued for a long time in a very
dusty environment, however, hard errors can result
from a damaged diskette surface.
o Random electrical noise ranging in time from a few
microseconds to a few milliseconds can also cause
read.errors. Spike noise generated by a switching
r e g u l a t o r , p a r t i c u l a r l y one that has s h o r t
switching intervals, deteriorates the signal-to-
noise ratio, and increases the number of re-read
operations for data recovery. It is necessary,
therefore, to make an adequate check on the noise
levels of the DC power supplies to the drive and
frame grounding.
o Written data or diskettes may have so small a
defect as cannot be detected by a data check
during write operation.
o F i n g e r p r i n t s or o t he r f o r e i g n mat t er on a w r i t t e n
d i s k e t t e can a l s o c a us e a t e m p o r a r y e r r o r .
I f
f o r e i g n m a t t e r i s l e f t on a w r i t t e n d i s k e t t e f o r a
l ong t i me, i t can adhere to the d i s k e t t e , p o s s i b l y