Reliability Specifications; Read Error Rates; Bit Jitter; Media Defects - Seagate ST251 Product Manual

1.7 RELIABILITY SPECIFICATIONS
1.11.2 HANDLING PRECAUTIONS
MTBF:
PM:
MTTR:
Service life:
20,000 Power-on hours
(Sea level, 25°C ambient temp.)
Not required
30 minutes
5 years
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After unpacking, and prior to system integration, the drive is exposed
to potential handling and ESD hazard.
Do not touch the PCB edge-connectors, board components or the
printed curcuit cable without observing static-discharge precautions.
Handle the drive by the frame only.
1.7.1 READ ERROR RATES
Always rest the drive on a padded surface until it is mounted in the
host system.
Recoverable Read Errors:
Nonrecoverable Read Errors:
Seek Errors:
1 per 1010 bits read
1 per
1012
bits read
1 per
106
seeks
1.11.3 SHIPPING ZONE
1.7.1.1 BIT JITTER
Bit jitter reduction determines the relationship between the leading
edge of read data and the center of the data wi ndow.
The specified read error rates are based on the following bit jitter
specifications: the data separator must provide at least -40 dB of bit
jitter reduction at 2F with an offset error of less than 1.5 nsec. shift
from the center of the data window.
1.7.2 MEDIA DEFECTS
A media defect is a read error when the data, which has been correctly
written, cannot be recovered within 16 retries.
A printout will be provided with each drive shipped listing the locations
of any defect by head, cylinder, sector and byte. It will also specify
the number of bytes from index. For MFM this will be based on 1.6
psec.lbyte. RLL encoding is based on 1.056 psec.lbyte.
A single media defect may be up to 16 bits long. Cylinders 0,1,2 and
3 will be free of defects.
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Upon power-down, the read/write heads will automatically move to
the shipping zone. All portions of the head/slider assembly will park
inboard of the maximum data cylinder. When power is applied, the
heads will recalibrate to Track
0.
The heads may also be parked in the shipping zone by issuing a seek
command to the maximum data cylinder plus one (820).
1.12 AUTO-TRUNCATION
The drive will enter the auto-truncation mode if the controller issues
an excessive number of step pulses, which would place the read/write
heads outward beyond Track
0
or inward beyond the maximum data
cylinder plus one (beyond 820).
With auto-truncation active, the drive will ignore additional pulses,
take control of the actuator, and recalibrate the heads to Track
0.
Caution:
If the controller is still issuing step pulses after the drive
issues Seek Complete from auto-truncation mode, the drive will either
reenter auto-truncation mode if Direction-In is false, or step the re-
maining cylinders if Direction-In is true.
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