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
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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