ISO/IEC 15731:1998 情報技術—情報交換用の12,65 mm幅の磁気テープカセット—ヘリカルスキャン記録—DTF-1フォーマット | ページ 5

4.1

Absolute block number

A number N allocated to each block, indicating that the block is the Nth block from the beginning of the Logical volume containing it.

4.2

a.c. erase

A process of erasure utilizing alternating magnetic fields of decaying intensity.

4.3

algorithm

A set of rules for transforming the logical representation of data.

4.4

Append file

A new file added from the End of Data (EOD) of a Logical volume.

4.5

Append volume

A Logical volume added after the last Logical volume recorded on the cassette.

4.6

Average Signal Amplitude

ASA

The average peak-to-peak value of the signal output of a read head measured over a minimum of 1,40 mm of track, exclusive of missing pulses.

4.7

azimuth

The angular deviation, in degrees of arc, of the recorded flux transitions on a track from the line normal to the track centreline.

4.8

back surface

The surface of the tape opposite to the magnetic coating used to record data.

4.9

bit cell

A distance along the track allocated for the recording of a Channel bit.

4.10

block

A unit of data which is sent to the tape controller when a single write command is executed.

4.11

Block Management Table

BMT

A table included in each Track Set to manage blocks contained in that Track Set.

4.12

byte

An ordered set of bits acted upon as a unit.

4.13

cassette

A case containing magnetic tape stored on twin reels.

4.14

compressed data

A representation of host-transmitted data after transformation by a data compression algorithm.

4.15

Control Track

A track used for recording the servo control signals.

4.16

flux transition position

That point along a track on the magnetic tape that exhibits the maximum free-space flux density normal to the tape surface.

4.17

flux transition spacing

The distance along a track between successive flux transitions.

4.18

Logical track set ID

The track set ID assigned to each track set containing data received from the host.

4.19

Logical volume

A data entity received by the generating system from the host.

4.20

magnetic tape

A tape which will accept and retain the magnetic signals intended for input, output, and storage purposes.

4.21

Master Standard Reference Tape

MSRT

A tape selected as the standard for Signal Amplitude, Reference Field, Resolution and Signal to Noise Ratio (S/N).

Note 1 to entry: The Master Standard Reference Tape has been established at SONY Corporation.

4.22

physical recording density

The number of recorded flux transitions per unit length of track, specified as flux transitions per millimetre (ftpmm).

4.23

Reference Field

RF

The Typical Field of the MSRT. There are two Reference Fields:

RF1 is that for a helically recorded track

RF2 is that for a longitudinally recorded track.

4.24

Secondary Standard Reference Tape

SSRT

A tape the performance of which is known and stated in relation to that of the MSRT.

Note 1 to entry: Secondary Standard Reference Tapes can be ordered under the Number SSRT-DTF-1, from the Sony Corporation, Magnetic Product Group, Data Media Sales Division, 6-7-3S Kitashinagawa, Shinagawa-ku, TOKYO 141, Japan. In principle such tapes will be available for a period of 10 years from the publication of the International Standard. However, by agreement between ISO and Sony Corporation, this period may be shortened or extended to take account of demand for such SSRTs.

It is intended that these SSRTs be used for calibrating tertiary reference tapes for use in routine calibration.

4.25

Standard Reference Amplitude

SRA

The Average Signal Amplitude derived from the MSRT, using the appropriate Test Recording Current and the appropriate physical recording density. There are three SRAs: SRA1 is derived from a helically recorded track, recorded at 3 201 ftpmm with TRC1. SRA2 is derived from a longitudinally recorded track at 20,75 ftpmm with TRC2. SRA3 is derived from a helically recorded track, recorded at 800,3 ftpmm with TRC1.

Traceability to the SRAs is provided by the calibration factors supplied with each Secondary Standard Reference Tape.

4.26

Standard Reference Current (Ir)

The current that produces a Reference Field. There are two Irs:

Irl is the current that produces RF1 on a helically recorded track.

Ir2 is the current that produces RF2 on a longitudinally recorded track.

4.27

Tape Reference Edge

The lower edge of the tape when the magnetic coating is facing the observer and the supply reel is to the observer’s right.

4.28

Test Recording Current

TRC

The current used to record an SRA. There are two Test Recording Currents:

TRC1 is 1,1 times Irl

TRC2 is 1,0 times Ir2

4.29

track

A narrow, defined area on the tape along which a series of magnetic transitions may be recorded. A track may be parallel to the Tape Reference Edge or at an angle to it.

4.30

track angle

The angle between the centreline of a helically recorded track and the Tape Reference Edge.

4.31

Track Set

A set of four consecutive helical tracks uniquely identified by a track set identification.

4.32

Typical Field

TF

There are two TFs:

In the plot of the ASA against the recording field:

TF1 is the minimum recording field giving an ASA equal to 90 % of the maximum ASA at the physical recording density of 3 201 ftpmm on a helically recorded track.

TF2 is the value of the recording field for which the increase of ASA resulting from an increase of 1 dB of the recording field falls to 0,5 dB at the physical recording density of 20,75 ftpmm on a longitudinally recorded track.

4.33

Unique Identifier

UID

An unambiguous value uniquely distinct from every other UID.

4.34

word

A group (or set) of four 8-bit bytes, numbered 0 to 3, byte 3 being the most significant.