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Theory of operations

Chapter 7

STT20000N Product Manual

Page 51

Theory of operations

Overview

The STT20000 SCSI minicartridge drive is a low-cost, high-performance TR-5
minicartridge tape drive that is ideal for standalone users or small network computer
systems. With capabilities of up to 10 to 20 Gbytes, depending upon media and data
compression, the drive offers quick, efficient backup and restore operations. Its
unique FastSense

TM

 feature automatically selects the appropriate transfer rate—

1,000, 733, or 489 Kbytes/sec—depending on the speed of the operating system.

The STT20000 SCSI minicartridge drive is based on proven Seagate designs,
Seagate firmware, and the latest component technologies. This drive uses second
generation custom LSI for efficient circuit layout and increased reliability for low
power consumption. The drive also uses flash EEPROM devices for easy firmware
upgrades.

This chapter describes the drive in more detail and explains implementation specific
information.

Drive configurations

The drive may be configured as Standard (STT20000N) or NS (STT20000N-C). The
NS configuration has all the features of the Standard drive with the following
additions:

• 

Read While Write(RWW) tape head

• 

Hardware data compression

• 

Larger (2-Mbyte) DRAM buffer

Block diagrams

The electronics of the SCSI minicartridge drive are laid out on one main printed
circuit board (PCB).

• 

Figure 7-1a and 7-1b are simplified block diagrams of the standard and NS
drives, respectively.

7

Содержание STT20000N

Страница 1: ... STT20000N STT20000N C SCSI Minicartridge Drives standard and NS 20 versions Product Manual ...

Страница 2: ...re trademarks or registered trademarks of their owners Seagate reserves the right to change without notice product offerings or specifications Seagate Technology provides this manual as is without warranty of any kind either expressed or implied including but not limited to the implied warranties of merchantability and fitness for a particular purpose Seagate Technology assumes no responsibility f...

Страница 3: ...a different outlet so that the computer and receiver are on different branch circuits If necessary you should consult the dealer or an experienced radio television technician for additional suggestions You may find the following booklet prepared by the Federal Communications Commission helpful How to Identify and Resolve Radio TV Interference Problems This booklet Stock No 004 000 00345 4 is avail...

Страница 4: ...o right is conveyed to reproduce or translate any item herein disclosed without express written permission from Seagate Technology Seagate Technology provides this manual as is without warranty of any kind either expressed or implied including but not limited to the implied warranties of merchantability and fitness for a particular purpose Seagate Technology reserves the right to change without no...

Страница 5: ...tions 11 Drive performance specifications 12 Environmental requirements 13 Reliability 14 Mean Time Between Failures 14 Mean Time To Repair 14 Recommended tapes 15 Regulatory compliance 15 Installation 17 Introduction 17 Handling guidelines 17 Installation overview 17 Setting jumpers 18 SCSI device address jumpers 19 Parity 19 SCSI terminator enable 19 Terminator power 20 Installing the drive 21 M...

Страница 6: ... 33 SCSI 1 status codes 33 SCSI 1 message codes 34 SCSI 1 commands 35 ANSI X3 131 CONFORMANCE STATEMENT SCSI 1 36 General features 36 Commands 36 Messages 37 Vendor unique commands 37 SCSI 2 interface 37 SCSI 2 status codes 37 SCSI 2 message codes 38 SCSI 2 commands 38 ANSI X3 T92 conformance statement SCSI 2 40 SCSI 2 general features 40 SCSI 2 commands 40 SCSI 2 messages 41 SCSI 2 vendor unique ...

Страница 7: ... Randomization 49 Theory of operations 51 Overview 51 Drive configurations 51 Block diagrams 51 Mechanics 53 Cartridge load mechanism 53 Capstan drive motor assembly 53 Chassis 53 Control circuits 53 Head design 54 Flash EEPROM 54 Sensors and switches 54 Media Travan minicartridges 55 Read While Write 56 ALDC data compression 56 Glossary 57 Acronyms and units of measurement 60 Acronyms and abbrevi...

Страница 8: ...Table of Contents Page viii STT20000A Product Manual Notes ...

Страница 9: ... Data compression is available within the Seagate Backup Exec software package for DOS and Windows and typically provides for a 2 1 compression ratio The compression ratio is dependent on the specific system and the nature of the files being compressed Using FastSenseTM a unique Seagate feature the STT20000 SCSI minicartridge drive automatically senses the fastest available data transfer rate of t...

Страница 10: ...an TR 5 media The drive offers electronically erasable programmable read only memory flash EEPROM which enables qualified Seagate OEMs to download revised firmware to the drive With the availability of greater capacity disk drives and the growth of small networks the need for cost effective high capacity SCSI storage has grown The STT20000 SCSI minicartridge drives are ideal for high end stand alo...

Страница 11: ...TT20000N Product Manual Page 3 Figure 1 1 STT20000 SCSI minicartridge internal drive 3 5 inch mounting configuration Figure 1 2 STT20000 SCSI minicartridge internal drive with mounting brackets 5 25 inch mounting configuration ...

Страница 12: ...ble data transfer rate 1 000 733 or 489 Kbyte sec Single ended SCSI connection with these features Embedded full LSI high speed SCSI controller Software selectable synchronous or asynchronous SCSI data transfer High performance SCSI burst transfer rate of 5 Mbyte sec with 512 Kbyte 2 Mbyte on the STT20000N C NS 20 drive on drive data buffer to facilitate the most efficient use of the host computer...

Страница 13: ... little more than a decade storage capacities have increased from some 60 megabytes Mbyte on 9 tracks QIC 24 1982 to the 20 Gbyte capacity achievable with the STT20000 SCSI minicartridge drive on a single Travan TR 5 cartridge The streaming tape intelligence in this minicartridge drive provides a continuous tape motion with an uninterrupted precisely coordinated flow of data to and from the minica...

Страница 14: ... control of the host computer s operating system Compatibility with a wide range of software is also an important consideration in system integration The drive requires any one of the following operating environments DOSTM version 5 0 or later Microsoft WindowsTM 3 1 or later Microsoft Windows 95 or Windows NT The drive operates with many of the popular backup software applications such as Seagate...

Страница 15: ... cabling requirements and connector pinouts 4 Drive operation Explains drive operation maintenance and troubleshooting 5 SCSI interface Lists general information about the SCSI interface See Note below 6 Tape format Provides an overview of the QIC 3220 MC tape format 7 Theory of operation Details the functional operation of various assemblies of the SCSI drive Appendix A Glossary Defines key terms...

Страница 16: ...Chapter 1 Introduction Page 8 STT20000A Product Manual Notes ...

Страница 17: ...ded tapes Tape capacities and formats Regulatory compliance Physical specifications The physical specifications of the STT20000 SCSI minicartridge drive are listed in the following table Specification Drive for 3 5 Inch Mount Drive for 5 25 Inch Mount Height 1 0 in 25 mm 1 7 in 43 mm Width 4 0 in 102 mm 5 87 in 149 1 mm Length 6 2 in 157 5 mm 6 36 in 161 5 mm Weight 1 0 lbs 0 5 kg 1 5 lbs 0 7 kg F...

Страница 18: ...T20000N 3 5 Inch mount general dimensions 4 00 in 101 6 mm 6 36 in 161 5 mm 0 157 in 4 mm 4 00 in 101 6 mm 1 00 in 25 4 mm Figure 2 2 STT20000N 5 25 Inch mount general dimensions 1 685 42 8mm 5 87 149 0mm 0 20 5 0mm 0 86 21 8mm 5 76 146 4mm 5 49 139 4mm DRIVE ACTIVE GREEN ...

Страница 19: ...nd are nominal values Specification Measurement DC Voltage 12 VDC 5 VDC Voltage Tolerance 10 5 Operational Current 2 0 amps 1 0 amp Standby Current 0 2 amp 0 6 amp Peak 2 2 amps max Power Sequence None None Ripple peak to peak 100 mV 100 mV Power use nominal 15 Watts excluding surge 15 Watts excluding surge The following table lists pin assignments for the power connector for the drive Pin Assignm...

Страница 20: ...essed Data transfer rate 489 733 1 000 Kbyte second FastSense TM Tape speed Read Write Search Rewind 46 70 or 94 ips 90 ips maximum Recording method Serpentine Recording format QIC 3220 MC Recording code 1 7 RLL Error recovery Reed Solomon ECC Recording unrecoverable errors Less than 1 in 1015 data bits Head configuration Wide write narrow read Recording media 1650 Oe 740 Travan TR 5 Cartridge siz...

Страница 21: ...ative humidity 20 to 80 non condensing1 5 to 95 non condensing2 Maximum wet bulb temperature 78 8 F 26 C No condensation Altitude 1 000 to 15 000 feet 1 000 to 50 000 feet Vibration Peak to Peak Displacement 0 005 in max 5 to 44 3 Hz 0 1 in max 5 to 17 Hz Peak Acceleration 0 50 g max 44 3 to 500 Hz 1 5 g max 17 to 500 Hz Acoustic level operational A wt sum 55 dBA maximum measured in suitable enclo...

Страница 22: ...on operational time as operational time increases above 20 of the power on time the MTBF is reduced conversely as the operational time is reduced the MTBF increase as an example at a operational duty cycle of 12 the STT20000 MTBF can equal 250 000 hours Note Seagate does not warrant the stated MTBF as representative of any particular unit installed for customer use The failure rate quoted here is ...

Страница 23: ...EINLAND EN 60 950 IEC 950 UL 1950 Canadian Dept of Communications Class B EN55022 CISPR 22 with additional CE Mark test req Class B FCC Class B Part 15 Use the STT20000 SCSI minicartridge drives only in equipment where the combination has been determined to be suitable by an appropriate certification organization for example Underwriters Laboratories Inc or the Canadian Standards Association in No...

Страница 24: ...Chapter 2 Specifications Page 16 STT20000A Product Manual Notes ...

Страница 25: ...n electrostatic grounding strap perform the installation at a static safe workstation If one is not available follow these guidelines as you install the interface card and drive unit Work in an uncarpeted area To protect the drive and interface card from static electricity DO NOT remove either the drive or the card from its anti static bag until you are ready to install it Before you remove the dr...

Страница 26: ...you are mounting the drive Setting jumpers Figure 3 1 illustrates the location of the jumpers on the bottom of the drive Figure 3 1 Location of drive jumpers SCSI CONNECTOR SCSI PIN 1 POWER CONNECTOR NOTE Bottom of drive shown JUMPER BLOCK PIN 1 The following settings should be checked prior to installation Figure 3 2 shows the jumper configurations for the various SCSI device addresses IDs and fo...

Страница 27: ...e effect or a SCSI Bus Reset must be received If the default address setting ID is correct for your system and you do not choose to change any other options go to the following section that explains how to install the drive unit If you need to change any default settings refer to Figure 3 2 and the appropriate following section make the changes and then go to the following section that explains ho...

Страница 28: ...on and does not require the use of terminating resistor packs Terminator power Terminator power 5 volt is enabled by default Caution If the jumper is installed be careful not to short the TERMPWR signal to ground The drive contains a terminator power fuse to prevent damage to drive components in case the terminator power is shorted If terminator power is enabled and the SCSI cable is connected ups...

Страница 29: ...he previous text under Configuring the Drive 4 Attach any special mounting hardware to the drive that your system might require Refer to the manual that you received with your computer for requirements 5 Locate the mounting screw holes in the drive brackets Each side contains two sets of holes Use the set that aligns the drive properly within the drive bay 6 Slide the tape drive into the computer ...

Страница 30: ... drive inoperative 10 Replace the computer cover and reconnect any peripherals that you disconnected during the installation Mounting dimensions Figures 3 4 and 3 5 respectively illustrate the location of the mounting holes for the internal drive without and with mounting brackets Figure 3 4 Mounting hole locations for internal drive 6 36 in 161 5 mm 2 382 in 60 mm 0 984 in 25 mm 3 543 in 90 mm 2 ...

Страница 31: ...ectors The drive provides standard single ended SCSI transmission ANSI SCSI standards specify the technical requirements for correctly cabling and connecting single ended devices Either 50 pin flat cable or 25 signal twisted pair cable with a maximum length of 6 meters 19 feet may be used to connect the drive to its SCSI host adapter output If twisted pair cabling is used connect the twisted pairs...

Страница 32: ... terminator power to the cable must have VTERM 4 25 to 5 25 VDC 900 milliamps minimum source drive capability When TERMPWR matches the above values the voltage of released signal lines must be at least 2 5 VDC When a driver asserts a line and pulls it to 0 5 VDC the current available to the signal line driver may not exceed 48 milliamps The first two terminators may only supply 44 8 milliamps of t...

Страница 33: ...for this single ended connector are listed in the following table Note All odd pins except pin 25 are connected to signal ground at the drive Pin 25 is left open A signal name or abbreviation preceded by a dash indicates that the signal is active low Pin Assignment 2 DB 0 4 DB 1 6 DB 2 8 DB 3 10 DB 4 12 DB 5 14 DB 6 16 DB 7 18 DB P 20 GROUND 22 GROUND 24 GROUND 26 TERMINATOR POWER 28 GROUND 30 GRO...

Страница 34: ...drive supply is available on the SCSI connector as a terminator power option This pin is connected to the 5V through a diode The option is a hardware jumper on the rear PCB of internal drives with terminator power disabled as a factory default 2 ANSI defines RST as a bi directional pin On the drive RST is input only ...

Страница 35: ...nel LED Using cartridges Loading revised firmware updating flash EEPROM Drive maintenance and troubleshooting Front panel LED operation The front panel of the Travan drive contains the cartridge opening and one amber light emitting diode LED This LED is lit when the tape is NOT at the beginning of the tape Thus the LED shows tape movement when lit Figure 4 1 shows the front panel of the internal d...

Страница 36: ...idge is inserted it is held firmly in place by the drive s positive locking mechanism Caution DO NOT remove a tape cartridge while the drive is active Complete any tape operations and wait until the amber LED is OFF before removing the cartridge To load a cartridge insert it with the metal base plate down and the tape access door facing into the drive Figure 4 2 illustrates the loading of a cartri...

Страница 37: ...r locked position Figure 4 5 Write protect switch in locked position To return a cartridge to the writeable state push the switch toward the end of the cartridge or to the unlocked position Loading revised firmware from a Seagate firmware cartridge The STT20000 SCSI minicartridge drive uses flash EEPROM Flash EEPROM enables you to download new firmware when revisions to firmware are released Firmw...

Страница 38: ... OFF THE DRIVE AT THIS TIME If a power interruption occurs the firmware may not be loaded correctly and the drive may not operate properly If a problem occurs during the firmware loading process the LED on the front panel goes out In that case the firmware upgrade cartridge may be defective or the drive may not be operating correctly If after a repeat loading of the firmware cartridge the same con...

Страница 39: ...guidelines to help ensure that your drive provides long reliable service Operate the drive in a clean dust free environment Never apply a lubricant to the drive Generally Travan drives are highly reliable and require little user maintenance For normal operations cleaning once per month is quite adequate For new cartridges clean the head after two hours of tape movement Thereafter the drive can be ...

Страница 40: ...e 2 Turn off all power to the computer and drive Wait for the computer to power down and then start over 3 Try a different tape preferably one that has never been used 4 Check all cable connections for proper contact 5 Clean the tape drive head as previously instructed Then try the operation again If problems persist contact your tape drive supplier or Seagate technical support at US and Canada 1 ...

Страница 41: ...atus codes message codes and commands Refer to Chapter 3 for specific SCSI cabling and connector information Note Refer to the SCSI Minicartridge Drive SCSI Manual P N 10001652 002 for detailed information about the SCSI interfaces That manual includes an alphabetically arranged summary of the STT20000 SCSI minicartridge drive SCSI commands SCSI 1 interface The SCSI 1 interface for the drive compl...

Страница 42: ... Message Reject In Out 08h No Operation Out 09h Message Parity Error Out 0Ah Linked Command Complete In 0Bh Linked Command Complete with Flag In 0Ch Bus Device Reset Out 80h Identify When sent by host disables Disconnect Reconnect In Out C0h Identify Enable Disconnect Reconnect Out 01h Extended Message In Out Direction In Drive to host Out Host to Drive Supports only one extended message SYNCHRONO...

Страница 43: ...TE 0Ch V SEEK BLOCK 0Dh V PARTITION 10h M WRITE FILEMARKS 11h O SPACE 12h E INQUIRY 13h O VERIFY 15h O MODE SELECT 16h O RESERVE UNIT 17h O RELEASE UNIT 19h O ERASE 1Ah O MODE SENSE 1Bh O LOAD UNLOAD 1Dh O SEND DIAGNOSTIC 1Eh O PREVENT ALLOW MEDIUM REMOVAL 3Bh WRITE DATA BUFFER 3Ch READ DATA BUFFER 40h CHANGE DEFINITION M Mandatory Command O Optional Command E Extended Command V Vendor Unique Comm...

Страница 44: ...s Fixed and variable block transfer lengths Hard reset Synchronous data transfer Parity implemented switch option Space blocks filemarks sequential filemarks and EOD Supports third party reservation Commands Change Definition Request Sense Erase Reserve Unit Inquiry Rewind Load Unload Seek Block Mode Select Send Diagnostic Mode Sense Space Prevent Allow Media Removal Test Unit Unit Ready Read Veri...

Страница 45: ...mand Complete No Operation Vendor unique commands Seek Block Partition Request Block Address SCSI 2 interface The SCSI 2 interface for the SCSI Minicartridge drive conforms with the ANSI X3 T92 standard The following three tables list the status codes message codes and commands for this interface SCSI 2 status codes 4 bit Status Code Bits 4 3 2 1 0 Definition 0 0 0 0 X Good Status 0 0 0 1 X Check ...

Страница 46: ... 0Ah Linked Command Complete In 0Bh Linked Command Complete with Flag In 0Ch Bus Device Reset Out 80h Identify When sent by host disables Disconnect Reconnect In Out C0h Identify Enable Disconnect Reconnect In Out 01h Extended Message In Out Direction In Drive to host Out Host to Drive Supports only one extended message SYNCHRONOUS DATA TRANSFER REQUEST SCSI 2 commands Code Type Command 00h M TEST...

Страница 47: ...SPACE 12h M INQUIRY 13h O VERIFY 15h M MODE SELECT 16h M RESERVE UNIT 17h M RELEASE UNIT 19h M ERASE 1Ah M MODE SENSE 1Bh O LOAD UNLOAD 1CH O RECEIVE DIAGNOSTIC RESULTS 1Dh M SEND DIAGNOSTIC 1Eh O PREVENT ALLOW MEDIUM REMOVAL 2Bh O LOCATE 34h O READ POSITION 3Bh O WRITE DATA BUFFER 3Ch O READ DATA BUFFER 40h O CHANGE DEFINITION 4Ch O LOG SELECT 4Dh O LOG SENSE ...

Страница 48: ... and variable block transfer lengths Hard reset Synchronous data transfers Parity implemented jumper option Space blocks filemarks sequential filemarks and EOD Supports third party reservation Log Sense and Log Select for managing soft errors reporting SCSI 2 commands Change Definition Receive Diagnostic Results Erase Release Unit Inquiry Request Block Address Load Unload Request Sense Locate Rese...

Страница 49: ...tion SCSI 2 messages Save Data Pointer Linked Command Complete Disconnect Linked Command Complete with flag Message Reject Initiator Detected Error Identify Synchronous Data Transfer Request Abort Message Parity Error Bus Device Reset Command Complete No Operation SCSI 2 vendor unique commands Seek Block Partition Request Block Address ...

Страница 50: ...pports read while write can be detected by requesting the available Log Sense pages Log Sense page code 0 then noting support for Log Sense page 2 Write Error Counts The Log Sense page code 2 parameter codes for write errors are listed in the following table Parameter Code Length in Bytes Name 0002 4 Total Rewrites 8010 4 Rewrites even tracks 8011 4 Rewrites odd tracks The total rewrite count is i...

Страница 51: ...de Sense page 0Fh Data Compression is present and the DCC bit is set the drive supports hardware data compression A second method would be to request Mode Sense page 0Fh Data Compression If the drive rejects the request or the DCC bit is not set then hardware data compression is not present The Mode Select Sense page code 10 parameter codes for data compression are listed in the following table Bi...

Страница 52: ... ALDC algorithm prior to writing to the medium when DCE bit is one A DCC bit of zero indicates the Drive does not support data compression This is a non changeable field A Data Decompression Enable DDE bit of one indicates that data decompression is to be enabled A DDE bit of zero indicates data decompression is disabled Normally DDE is always set on tape drives that support hardware data compress...

Страница 53: ...10 0 Gbyte on the data partition of 740 foot long 0 315 inch 8 0 mm wide Travan TR 5 tape Using data compression this capacity is up to twice the native storage capacity The recording format and partitioning support Quick File Access QFA Track positions The centermost track is called the Directory Track and has larger guard bands on both sides of it to allow it to be written without interfering wi...

Страница 54: ...Logical numbering does not relate to the blocks physically recorded on the tape rather this type of numbering is the block numbering system used by the host computer Often the host system operates with logical blocks that are a different size from the 512 byte blocks that are physically recorded on the tape The host blocks can be larger or smaller than 512 bytes and can also be fixed or variable F...

Страница 55: ...ewritten in its entirety at the beginning of the following track Frames are not split around corner turns The general frame layout 108 data blocks and 20 ECC blocks is illustrated in Figure 6 2 Figure 6 2 General frame layout Data Block 0 Data Block 1 Data Block 2 Data Block 107 ECC Block 0 ECC Block 1 ECC Block 19 The four types of frames are as follows Data frames contain data and information bl...

Страница 56: ...ion blocks Filemark blocks Setmark blocks and Cancelmark blocks contain specific types of information Filemark blocks are physical blocks written to tape in response to a host WRITE FILEMARKS command Setmark blocks are physical blocks written to tape in response to a host WRITE SETMARKS command Cancelmark blocks are physical blocks written to tape under firmware control Filler blocks contain no va...

Страница 57: ... Oersted media write equalization provides the benefit of compatibility with Magneto Resistive MR heads MR heads are prone to saturation by low frequency flux with high energy content Equalization redistributes this energy to higher frequencies and eliminates the problem Randomization To reduce problems resulting from long strings of repetitive data with a bad peak shift or amplitude characteristi...

Страница 58: ...Chapter 6 Tape format Page 50 STT20000A Product Manual Notes ...

Страница 59: ...te designs Seagate firmware and the latest component technologies This drive uses second generation custom LSI for efficient circuit layout and increased reliability for low power consumption The drive also uses flash EEPROM devices for easy firmware upgrades This chapter describes the drive in more detail and explains implementation specific information Drive configurations The drive may be confi...

Страница 60: ...z CRYSTAL READ WRITE TAPE HEAD CAPSTAN MOTOR STEPPER MOTOR MOTOR CONTROLLER 512KB D R A M SCSI INTERFACE SENSORS Figure 7 1b Simplified Block Diagram of the STT20000N C Drive DIGITAL CONTROL ASIC 256KB EEPROM 5VOLT 188uP 20MHz 40MHz CRYSTAL READ WRITE R W W TAPE HEAD CAPSTAN MOTOR STEPPER MOTOR MOTOR CONTROLLER 2MB D R A M SCSI INTERFACE SENSORS ALDC 1 H W DATA COMPRESSION ...

Страница 61: ...dge is loaded against the cartridge drive roller which exerts a net radial dynamic force of 18 to 26 ounces The motor is a brushless DC drive motor with integral capstan which is designed to provide maximum reliability The motor operates from the 12V nominal supply and moves the tape at speeds from 35 to 100 inches per second IPS Chassis The drive mechanism is mounted in a molded frame that provid...

Страница 62: ...f the head also results in exceptional wear characteristics resulting in stable performance throughout the life of the drive Flash EEPROM Because the drive uses flash EEPROM Electronically Erasable Programmable Read Only Memory the drive firmware can be easily upgraded when new revisions of the firmware are released The circuitry includes 128 Kbyte of flash EEPROM Loading new firmware can be accom...

Страница 63: ...IC Wide minicartridges These small approximately 2 inches x 3 inches x 0 4 inch cartridges house 1650 Oersted Gamma Ferric Oxide magnetic tape Figure 7 2 shows a Travan minicartridge Figure 7 2 Travan Minicartridge The cartridge also provides write protection so that existing data on the cartridge is not overwritten A write protected cartridge allows the existing data to be read but does not allow...

Страница 64: ...ed good and the checking process begins again on the next block of data If the data fails the data block is deemed bad and is re written The drive will only allow the data to be re written 16 times before aborting the write and posting an error to the host ALDC data compression The STT20000N C version of the drive also provides hardware data compression This feature is enabled at power on and can ...

Страница 65: ... 8 binary bits operated on as a unit Cancelmark A negative Filemark or Setmark When a Cancelmark follows as the first block in the next frame after a Filemark or Setmark the drive when reading the tape will logically ignore the Cancelmark and the Filemark or Setmark it cancels Cartridge An enclosure containing magnetic tape wound on two coplanar hubs Control field A group of 8 bytes recorded befor...

Страница 66: ...aching end of the usable recording area in the forward direction File A logical unit of information Filler block A block containing no valid information in its data field Fixed Disk A non removable hard disk All data must be transferred to and from the disk via the computer Frame A group of 128 blocks forming a complete logical group Full high or full height Usually refers to a tape drive fitting ...

Страница 67: ...gap Tape Drive A peripheral storage device that records data onto removable tape cartridges Used to back up a disk drive See also Disk Drive Track A longitudinal area on the tape along which magnetic signals can be serially recorded Track ID block A block recorded in the Load Point and Early Warning regions to designate the track number Uncorrected Bit Error Rate The probability of a bit being in ...

Страница 68: ...Beginning of Media BOT Beginning Of Tape BPI Bits Per Inch CD Compact Disc CMOS Complementary Metal Oxide Semiconductor CSA Canadian Standard Association DMA Direct Memory Access ECC Error Correction Code ECMA European Computer Manufacturers Association EEPROM Electronically Erasable Programmable Read Only Memory EOD End of Data EOM End of Media EOT End Of Tape FCC Federal Communications Commissio...

Страница 69: ...e LSI Large Scale Integration MTBF Mean Times Between Failures MTTR Mean Time To Repair OEM Original Equipment Manufacturer PCB Printed Circuit Board QIC Quarter Inch Cartridge Drive Standards Incorporated RAM Random Access Memory RLL Run Length Limited SCSI Small Computer System Interface UL Underwriters Laboratories Inc VDC Volts Direct Current VDE Verband Deutscher Electrotechniker ...

Страница 70: ...weighted sound power reference one picowatt F Fahrenheit ft foot or feet g acceleration of a free falling body equal to 32 17 feet per second2 Gbyte gigabyte Hz Hertz in inch k kilo Kbyte kilobyte kg kilogram KHz kilohertz lb s pound s m meter M mega Mbits megabits Mbyte megabyte MHz megaHertz min minute mm millimeter ms millisecond RPM revolutions per minute V Volt W Watt ...

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