Seagate ST251 User manual

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ST251/ST251 R/ST277R
Product Manual
February 3, 1987
36035-001, Revision A
(, ~920 Disc Drive, Scotts Valley, CA 95066-4544, USA
Telephone: [phone]. Telex: 176455 SEAGATE SCVL
d5» Seagate

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Copyright Notice
This manual and all the material contained in it are copyrighted with
all rights reserved. This manual may not be copied, in whole or in
part, witholJt written consent of Seagate Technology.
Seagate reserves the right to change, without notice, the specifications
contained in this manual.
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ii ST251/251 R/277R Product Manual, Rev.A

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CONTENTS
1.0 SPECIFICATION SUMMARY .
1.1 Drive Capacity .
1.1.1 Unformatted Capacity .
1.1.2 Formatted Capacity .
1.1.3 Physical Organization .
1.2 Access Time Definition and Timing .
1.3 Step Pulse Period and Seek Method .
1.4 Functional Specifications .
1.5 Recording Methods .
1.6 Physical Specifications .
1.7 Reliability Specifications .
1.7.1 Read Error Rates .
1.7.1.1 Bit Jitter .
1.7.2 Media Defects .
1.7.2.1 ST251 .
1.7.2.2ST251R .
1.7.2.3 ST277R .
1.8 Environmental Specifications .
1.8.1 Ambient Temperature .
1.8.1.1 ST251 .
1.8.1.2 ST251R/277R .
1.8.2 Temperature Gradient .
1.8.3 Relative Humidity .
1.8.4 Altitude Limits .
1.8.5 Shock and Vibration Specifications .
1.8.5.1 Operating Shock .
1.8.5.2 Operating Vibration .
1.8.5.3 Nonoperating Shock .
1.8.5.4 Nonoperating Vibration .
1.9 DC Power Specifications .
1.9.1 Input Noise Ripple and Frequency .
1.9.2 UL/CSA Certification .
1.10 FCC Certification .
1.11 Mounting Requirements .
1.11.1 Shock Mounting Recommendations .
ST251 /251R/277R Product Manual, Rev.A
1-1
1-1
1-1
1-1
1-1
1-2
1-2
1-3
1-3
1-3
1-4
1-4
1-4
1-4
1-5
1-5
1-5
1-5
1-5
1-5
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1-6
1-6
1-6
1-6
1-6
1-7
1-7
1-8
1-10
1-10
1-10
1-11
1-11
iii

1.11.2 Handling Precautions .
1.11.3 Shipping Zone .
1.12 Auto-Truncation .
1.13 Typical Drive Timing .
2.0 DRIVE CONFIGURATION .
2.1 Drive Configuration Shunt J7 .
2.2 Drive Select .
2.2.1 Daisy-Chain/Radial Drive Configurations .
2.3 Write Fault Latch Options: JP1 and J7 .
2.4 DC-Unsafe Option: JP2 .
2.5 Precompensation .
2.6 Life-Test .
APPENDIX A. MFM/RLL FORMAT EXAMPLE .
1-13
1-131-131-14
2-1 (
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2-1 ~
2-2
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2-2 2-22-32-32-3
A-1
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iv ST251 /251R/277R Product Manual, Rev.A
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1) (LIST OF IllUSTRATIONS
Figure 1. Typical +12 VDC Start-Up Current Profile 1-9
Figure 2. Typical Power-On Sequence 1-9
Figure 3. Drive Mounting Dimensions 1-12
Figure 4. Read/Write Timing 1-14
Figure 5. Buffered-Seek Timing 1-15
Figure 6. Auto-Truncation Timing 1-15
Figure 7. Host/Drive Interface Connectors 2-1
2-4 ST251 /251R/277R Product Manual, Rev.A
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ST251 /251R/277R Product Manual, Rev.A v

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The latched operation has two configurations which are provided at
the J7 shunt, pins 5-6.
1. No jumper at J7: The Write Fault signal can only be cleared by a
power on/off cycle. Use of this option in conjuction with the DC-
Unsafe option is not recommended.
2. Pins 5-6 shorted at J7: The Write Fault signal can be cleared by
de-selecting the drive. When the drive is deselected, and the fault
condition is corrected, the Write Fault signal will be false.
2.4 DC-UNSAFE OPTION: JP2
JP2 has two jumper pads, and when a jumper is installed, a DC-unsafe
condition will cause a Write Fault to be sent to the interface. Use Fig-
ure 7on page 2-1 to locate JP2.
2.5 PRECOMPENSATION
The ST251/251R/277R do not require precompensation.
2.6 LIFE-TEST
This is a test function used during the manufacturing process and is
not recommended for field use. When pins 7-8 of J7 are shorted, the
stepper motor will continuously seek between Track 0 and the maxi-
mum cylinder and will ignore control signals sent via the interface.
vi ST251 /251R/277R Product Manual, Rev.A
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ST251 /251R/277R Product Manual, Rev.A 2-3

2.2 DRIVE SELECT
The Drive Select line enables the controller to select and address the
drive. Control cable interface options may use either a daisy-chain or
radial configuration.
Pins 15-16 shorted enables Drive Select 1
Pins 13-14 shorted enables Drive Select 2
Pins 11-12 shorted enables Drive Select 3
Pins 9-10 shorted enables Drive Select 4
2.2.1 DAISY-CHAIN/RADIAL DRIVE CONFIGURATIONS
The ST251/251R/277R can be configured in either a daisy-chain or
radial mode. The radial option is enabled by shorting pins 1 and 2 at
J7. The resistor termination pack must remain installed on any radially
configured drive.
In a daisy-chain configuration, the last drive in a chain must have the
resistor termination pack installed.
2.3 WRITE FAULT LATCH OPTIONS: JP1 AND J7
These options allow the user to configure the Write Fault reset to spe-
cific system requirements.
JP1 has three jumper pads, and is located adjacent to the 34-pin J1
connector. Figure 7on page 2-1 illustrates JP1 and indicates pin-1. J7
is located midway between the PCB edge-connectors (see "2.1 Drive
Configuration Shunt J7" on page 2-1).
STANDARD: 1 and 2 jumpered on JP1
Write Fault will be cleared when Write Gate is false. A Write Fault will
only occur when Write Gate is true.
LATCHED: 2 and 3 jumpered on JP1
This option will maintain Write Fault true after Write Gate goes false
and is recommended for controllers that do not edge-detect Write Fault.
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INTRODUCTION
This manual supports the ST251/251R/277R disc drives. It supercedes
and replaces the ST251 Product Manual, 36016-001, Rev. B.
2-2 ST251/251R/277R Product Manual, Rev.A ST251/251R/277R Product Manual, Rev.A vii

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2.0 DRIVE CONFIGURATION
The ST251/251R/277R may be configured for specific system require-
ments.
2.1 DRIVE CONFIGURATION SHUNT J7
J7 is a 16-pin right-angle shunt located midway between the J1 and J2
connectors. Use the provided shorting block(s) to enable the Drive
Select line and any options. Figure 7 illustrates J7 and indicates pin 1.
FIGURE 7: Host/Drive Interface Connectors
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DC power and
Pin Connector Assignments
Ir8008il
PIN POWER
1
+12 VOLTS
2+12 VOLTS RETURN
3+5 VOLTS RETURN
4+5 VOLTS
808000(0)
R~a~wq:X ~ ~~ r
rIF<Jult Test
Reserved
J7-16 PIN CONNECTOR
Shown with drive configured as DS-1
viii ST251 /251 R/277R Product Manual, Rev.A ST251 /251R/277R Product Manual, Rev.A 2-1

1-16 ST251 /251 R/277R Product Manual; Rev.A ST251 /251 R/277R Product Manual, Rev.A 1-1

1.2 ACCESS TIME DEFINITION AND TIMING FIGURE 5: Buffered-Seek Timing
1.3 STEP PULSE PERIOD AND SEEK METHOD
Access time is defined as the time from the leading edge of the first
step pulse received to Seek Complete (including settling). All seek
times are true statistical averages and are calculated with a step pulse
period of 10 jJsec. at nominal power and temperature.
- DIRECTION IN
-1 ~ 100 nsec. min.
-STEP
-1 ~ r-, 3 ~sec. min.
100 nsec. typo 200 ~sec. max.
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- SEEK COMPLETE : I L
~DON'T CARE~A STABLE ~DON'T CARE~
2~sec. min.
~ L1 0 ~sec. max.
100 nsec min. _11_ -I ~
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8 msec. max.
40 msec. max.
95 msec, max,
8.33 msec.
Track-to-Track:
Average:
Full-Stroke:
Average Latency:
- DRIVE SELECT I : I
I.• 40 msec. avg. ~I
95 msec. max.
The step signal is a 2jJsec. minimum width pulse which initiates read/
write head motion. The step pulse period determines the access
method. The number of pulses determines the seek length. The step
pulse period must be between 3jJsec. and 200jJsec.
Step pulses may be lost at periods greater than 200jJsec. For additional
information on step pulses and seek methods consult the Seagate
ST412 Interface Manual, (
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100 nsec. min-1 ~ 100 nsec. min-1 ~
FIGURE 6: Auto- Truncation Timing
-TRACK eJ
:. Excessive Step Pulses Recognized
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- SEEK
COMPLETE
9 msec. typo I •• ~I
:;;_r I _
((I•• 13 sec. max. ~I
1-2 ST251/251R/277R Product Manual, Rev.A ST251/251R/277R Product Manual, Rev.A 1-15

1.13 TYPICAL DRIVE TIMING
This section details typical ST251/251R/277R timing. Refer to the
Seagate ST412 Interface Manual for a general treatment of drive tim-
ing.
FIGURE 4: Read/Write Timing
• DRIVE SELECT
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1.4 FUNCTIONAL SPECIFICATIONS
ST251
ST251 R
ST277R
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Rotational Speed: 3,600 RPM ±0.5%
((Recording Density:
9,935 BPI
14,902 BPI
14,902 BPI
18
Flux Density:
9,935 FCI
9,935 FCI
9,935 FCI
Track Density:
777 TPI777 TPI777 TPI
Interface:
ST412
ST412
ST412
Recording Method:
MFM
RLL (2,7)
RLL (2,7)
Data Transfer Rate:
5.0 Mbits/sec. 7.5 Mbits/sec. 7.5 Mbits/sec.
- HEAD SELECT
1.5 RECORDING METHODS
1.6 PHYSICAL SPECIFICATIONS
The ST251 is designed to operate with the ST412 interface with MFM
encoding at 5.0 megabit/sec. data transfer rate.
Caution: Operation of an MFM drive with an RLL controller is not ap-
proved by Seagate.
1.63 inch. max. (41.4 mm)
5.77 inch. max. (146.1 mm)
8.00 inch. max. (203.2 mm)
2.75 Ibs. (1.25 Kg.)
The ST251R and ST277R are designed to operate with the ST412 in-
terface with Run Length Limited (2,7) encoding at 7.5 megabit/sec.
data transfer rate.
Height:
Width:
Depth:
Weight:
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--------------j"'j"----------
HJL40 nsec. min. /95 nsec. max.8 !lsec. max. I I
(Head Switching) n n n n n n n+MFM (RLL) VALID I U U U I ~ UQ~O~
-R-E-A-D-D-A-T-A---1-~ ------..,: -1 ~ 8 !lsec. max.
200 nsec. (write/read
(typ. bit cell) recovery)
-.-W-R-IT-E-G-A-T-E-------I ..,~
400 nsec. max. H)~r-50 . 150 nsec.
+MFM (RLL) WRITE DATA ~~ •• _
UJL200 nsec.Ir(typ. bit cell)
1-14 ST251 /251 R/277R Product Manual, Rev.A ST251 /251 R/277R Product Manual, Rev.A 1-3

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 (N
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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 0or 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.
1-4 ST251 /251R/277R Product Manual, Rev.A ST251 /251R/277R Product Manual, Rev.A 1-13

vertical resonant frequency of 25 Hz or lower. A minimum clearance
of 0.050 inches should be allowed around the entire perimeter of the
drive to allow for cooling airflow and motion during mechanical shock
or vibration. I
1.7.2.1 ST251
There will be no more than forty-two (42) defects total per drive.
FIGURE 3: Drive Mounting Dimensions
800 max
(2032)
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1682 ±01O
(42.72 ± 25)
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,031 ±.025
(0.78 ±.63)
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'.63 max
(414)
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There will be no more than forty-three (43) defects total per drive.
1.7.2.3 ST277R
There will be no more than sixty-five (65) defects total per drive.
---l1.B7+.03 I
(47.50±.76r
195 ±01O' I
(495 ± 251 -' 1- - I
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1.8.1 AMBIENT TEMPERATURE
100e to 45°e (500F to 113°F)
-400e to 600 (-400Fto 1400F)
Operati ng:
Nonoperati ng:
1.8 ENVIRONMENTAL SPECIFICATIONS
1.8.1.2 ST251 R/277R
1.8.1.1 ST251
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5.77 max.
(146.6)
, MOL;I\TII\G
) 1I(.)LES.·~4 on hot-:
tom. 4on each sIde
o-12LJ'\IC-2B (12X)
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3.12 ±.03 _ I(79.25 ± .76) l
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'5.50 ±.03
(139.7 ±.76j
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5875 1:. 010
(149.22 ± 25)
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1.8.2 TEMPERATURE GRADIENT
NOTE: The mounting screws must not extend
inside the mounting leet more than 0.125 inch,
measured lrom the outside surface 01 the loot.
Outside Surface
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Operating:
Nonoperating:
Operati ng:
Nonoperati ng:
150e to 450e (59°F to 113°F)
-400e to 60° HOoF to 140°F)
100e/hr. (18°F/hr.) max.
Below condensation
1-12 ST251 /251R/277R Product Manual, Rev.A ST251 /251R/277R Product Manual, Rev.A 1-5

1.8.3 RELATIVE HUMIDITY
Operating:
Maximum Wet Bulb:
Nonoperating:
1.8.4 ALTITUDE LIMITS
Operating:
Nonoperating:
8 to 80% noncondensing
26°C (78.8°F)
5 to 90% noncondensing
-1,000 ft to 10,000 ft
-1,000 ft to 30,000 ft
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It has been type tested and found to comply with the limits for a Class
B computing device peripheral in accordance with the specifications
in Subpart Jof Part 15 of FCC rules, which are designed to provide
reasonable protection against such interference in a residential instal-
lation. However, there is no guarantee that interference will not occur
in a particular installation. If this equipment does cause interference
to radio or television, which can be determined by turning the equip-
ment on and off, you are encouraged to try one or more of the following
corrective measures:
• Reorient the receiving antenna.
• Move the device to one side or the other of the radio or TV.
1.8.5 SHOCK AND VIBRATION SPECIFICATIONS
All shock and vibration specifications assume that the drive is mounted
in an approved orientation with the input levels at the drive mounting
screws.
Shock measurements are based on a 11 msec. half-sine wave shock
pulse. The nonoperating specifications assume that the read/write
heads are positioned in the shipping zone.
1.8.5.1 OPERATING SHOCK
Maximum shock without incurring physical damage or degradation in
performance: 10 G's.
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• Move the device farther away from the radio or TV.
• Plug the computer into a different outlet so that the receiver and
computer are on different branch outlets.
If necessary you should consult your dealer or an experienced radio/
television technician for additional suggestions. You may find helpful
the following booklet prepared by the Federal Comunications Com-
mission: How to Identify and Resolve Radio-Television Interference
Problems. This booklet is available from the Superintendent of Docu-
ments, U.S. Government Printing Office, Washington, DC 20402. Refer
to publication number 004-000-00345-4.
1.11 MOUNTING REQUIREMENTS
1.8.5.2 OPERATING VIBRATION
Maximum vibration, at the following frequencies, without incurring
physical damage or degradation in performance:
Freq.
5-22 Hz:
22-300 Hz:
300-22 Hz:
22-5 Hz:
Vibration
0.010 in. Displacement (double amplitude)
0.25 G Acceleration (peak)
0.25 G Acceleration (peak)
0.010 in. Displacement (double amplitude)
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The drive may be mounted horizontally with the PC Board down or on
either side. Mounting vertically on either end is a prohibited orienta-
tion. Refer to Figure 3on page 1-12 for mounting dimensions.
The drive should not be tilted front or back, in any position, by more
than 5°. For optimum performance the drive should be formatted in
the same position as it will be mounted in the host system.
1.11.1 SHOCK MOUNTING RECOMMENDATIONS
It is recommended that any external shock mounts between the drive
and the host frame be designed so that the composite system has a
1-6 8T251/251 R/277R Product Manual, Rev.A 8T251/251 R/277R Product Manual, Rev.A 1-11

1.9.1 INPUT NOISE RIPPLE AND FREQUENCY
The maximum permitted noise ripple is 100 mV (peak-to-peak) mea-
sured at the host system power supply across an equivalent 8 Qre-
sistive load on the + 12 Volt line and an equivalent 3 Qload on the
+5Volt line. The maximum permitted input noise frequency is 20 MHz.
1.9.2 ULlCSA CERTIFICATION
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1.8.5.3 NONOPERATING SHOCK
Maximum shock without incurring physical damage or degradation in
performance: 40 G's.
1.8.5.4 NONOPERATING VIBRATION
Maximum vibration, at the following frequencies, without incurring
physical damage or degradation in performance:
TheST251 is listed in accordance with UL478 and CSA C22.2 (0-M1982),
and meets all applicable sections of IEC 380 and VDE 0806/08.81, as
tested by TUV-Rheinland, North America.
1.10 FCC CERTIFICATION
WARNING
The ST251 is certified to comply with the limits for a Class B computing
device, pursuant to Subpart Jof Part 15 of FCC rules. Only devices
certified to comply with the Class B limits may be attached to this
peripheral. Operation with non-certified devices is likely to result in
interference to radio and television reception.
Radio and Television Interference
This equipment generates and uses radio frequency energy and if not
installed and used in strict accordance with the manufacturer's instruc-
tions, may cause interference to radio and television reception.
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Freq.
5-22 Hz:
22-300 Hz:
300-22 Hz:
22-5 Hz:
Vibration
0.020 in. Displacement (double amplitude)
0.50 G Acceleration (peak)
0.50 G Acceleration (peak)
0.020 in. Displacement (double amplitude)
1-10 ST251/251 R/277R Product Manual, Rev.A
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ST251/251 R/277R Product Manual, Rev.A 1-7

1.9 DC POWER SPECIFICATIONS FIGURE 1: Typical +12 VDC Start-Up Current Profile
Power may be applied or removed in any sequence without loss of
data or damage to the drive.
Typical seek currents are measured on a buffered one-third stroke
seek followed by two revolutions of non-seek time.
Maximum seek currents are measured on repetitive 3-track buffered
seeks with a one-half spindle rotation between each seek.
2015
5 msec. max. H
10
SECONDS
- SEEK COMPLETE
-----------....•(( (..(-------
II II 1 _
_ READY 20 msec. max·H
______ ~_-i(( ((
II I/~-----I
------
- TRACK 0
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FIGURE 2: Typical Power-On Sequence
(( ((
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DC ON
~12 sec. typo~
ROTATIONAL SPEED ~r;
REGULATED ±O.5% (
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~ 10 sec. typo ~
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13 Watts typo
11 Watts typo
0.7 Amps max. RMS
0.5 Amps typo RMS
±5% both seek and nonseek con-
ditions
1.4 Amps max. Peak
1.1 Amps max. RMS
0.9 Amps typo RMS
1.3 Amps max. RMS
1.0 Amps typo RMS
±5% both seek and nonseek con-
ditions
2.0 Amps
1.8 Amps max. Peak
1.1 Amps max. RMS
0.7 Amps typo RMS
+5VDC
Voltage Tolerance (inc. ripple):
+12 VDC
Voltage Tolerance (inc. ripple):
Nonseeking Current:
Seeking Cu rrent:
Nonseeking Current:
POWER
Seeking:
Nonseeking:
Max. Current at Power-Up:
Seeking Current:
Typical seeking/nonseeking current and power specifications assume
nominal voltages applied, 25°C ambient temperature, sea level and
spindle rotating.
Maximum (3 sigma max.) seeking/nonseeking current specifications
assume 10° C ambient temperature, 5.25 VDC and 12.6 VDC applied,
sea level and spindle rotating.
14 25 sec. max. al
1-8 ST251 /251 R/277R Product Manual, Rev.A ST251 /251 R/277R Product Manual, Rev.A 1-9