Cipher Data Products FloppyTape 525 Series Technical specifications

Series 525 FloppyTapeTM
Cartridge Tape Drive
Product Description

Section
1
1.1
1.2
1.3
1.4
2
2.1
2.1.1
2.1.2
2.2
2.2.1
2.2.2
2.2.3
2.3
2.3.1
2.3.2
2.3.3
2.3.4
3
3.1
3.2
3.3
3.4
4
4.1
4.2
4.3
4.4
4.5
4.6
4.7
4.8
5
5.1
5.2
5.3
5.4
5.5
5.5.1
5.5.2
TABLE OF CONTENTS
Page
INTRODUCTION •••••••••••••••••••••••••••••••••••••••••••.••••••• 1-1
Scope ••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 1-1
Terminology ••••••••••••••••••••••••••••••••••••••••••••••••••• 1-1
General Description •••••••••••••••••••••••••••••••••••••••••••• 1-3
Features ••••••.••••••••••••••••••••••••••••••••••••••••••••••• 1-3
SPECIFICATIONS & RELIABILITY ••••••••••••••••••••••••••••••••••• 2-1
Tape Specifications ••••••••••••••••••••••••••••••••••••••••••••• 2-1
Record ing Times •••.••••••••••..••••••••••••••••••••••••••• 2-1
Positioning •••••••••••••••••••••••••••••••••••••••••••••••• 2-1
Reliability •••.•••••••••••••••••••••••••••••••••••••••••••••••• 2-2
Mean Time Between Failures ••.••••••••••••••••••••••••••••• 2-2
Mean Time To Repair •••••••.••••••••••••••••••••••••••••••• 2-2
Preventive Maintenance ••••••••••••••••••••••••••••••••••••• 2-2
Data Integrity ••••••••••••••••••••••••••••••••••••••••••••••••• 2-3
Med ia •••••••••••••••••••••••••••.•••••••••••••••••••••••• 2-3
Recoverable Read Errors •••••••••••••••••••••••••••••••••••• 2-3
Non-Recoverable Read Errors •••••••••••••••••••••••••••••••• 2-3
Power Loss •••••••••••••••••••••••••••••••••••••••••••••••• 2-3
FUNCTIONAL CHARACTERISTICS •••••••••••••••••••••••••••••••••• 3-1
General Description •••••••••••••••••••••••••••••••••••••••••••• 3-1
Read/Write & Control Electronics •••••••••••••••••••••••••••••••• 3-1
Tape Drive Mechanism •••••••••••••••••••••••••••••••••••••••••• 3-3
Read/Write Head Positioning Mechanism •••••••••••••••••••••••••• 3-3
FUNCTIONAL DESCRIPTION •••••••••••••••••••••••••••••••••••••••• 4-1
Power Sequencing •••••••••••••••••••••••••••••••••••••••••••••• 4-1
Stream Selection ••••••••••••••••••••••••••••••••••••••••••••••• 4-1
Head Load/Motor On •.••••••••••••••••••••••••••••••••••••••••• 4-2
Seg ment Accessing ••••••••••••••••••••••••••••••••••••••••••••• 4-2
Step Out/Step In ••••••••••••••••••••••••••••••••••••••••••••••• 4-4
Read Operation •••••••••••••••••••••••••••••••••••••••••••••••• 4-4
Write Operation •••••••••••••••••••••••••••••••••••••••••••••••• 4-5
Recording Format •••••••••••••••••••••••••••••••••••••••••••••• 4-6
INTERF ACE SIGNALS •••••••••
Drive Interface •••••••••••
Interface Signal Levels ••••••••••••••••••••••••••••••••••••••••••
Input Control Signals •••••••••••••••••••••••••••••••••••••••••••
Output Control Signals ••••••••••••••••••••••••••••••••••••••••••
Da ta Line Signa Is ••••••••••••••••••••••••••••••••••••••••••••••
Read Data Signa1 ••••••••••••••••••••••••.•••••••••••••••••••
Write Data Signa1 ••••••••••••••••••••••••••••••••••••••••••
5-1
5-1
5-4
5-4
5-5
5-6
5-6
5-7
Cipher Data Products, Inc. reserves
the right to change specifications
without notice.
Copyright 1984
i

Section
6
6.1
6.2
6.3
6.4
6.5
7
7.1
7.2
7.3
8
8.1
8.2
8.3
8.4
8.5
8.6
8.7
8.8
8.9
8.10
9
9.1
9.2
9.3
9.3.1
9.3.2
9.4
9.4.1
9.4.2
9.4.3
9.4.4
9.4.5
9.4.6
9.5
9.5.1
9.5.2
9.5.3
9.6
9.6.1
9.6.2
9.6.3
TABLE
OF CONTENTS (Continued)
Page
PHYSICAL INTERFACE CONNECTION ••••••••••••••••••••••••••••••• 6-1
Interface Connector Locations .•••••••••••••••••••••••••••••••••• 6-1
Signal
Connector Dimensions •••••••••••••••••••••••••••••••••••• 6-1
Recommended Cables and Connectors ••••••••••••••••••••••••••••• 6-2
T ermina tion ••••••••••••••••••••••••••••••••••••••••••••••••••• 6- 2
Fra me Ground ••••••••••••••••••••••••••••••••••••••••••••••••• 6-2
PHYSICAL CHARACTERISTICS ••
Mechanical Dimensions ••••••
Weight ••••••..••.••••.•...•....•...••...••..•....•••.....•.•••
Mounting ..................................................... .
7-1
7..:1
7-1
7-1
ENVIRONMENTAL CHARACTERISTICS/POWER REQUIREMENTS ••••••• 8-1
Temperature •••••••••••••••••••••••••••••••••••••••••••••••••• 8-1
Humidity •••••••••••••••••••••••••••••••••••••••••••••••••••••• 8-1
Altitude •••••••••••••••••••••••••••••••••••••••••••••••••••••• 8-1
Vib ration ...................................................... 8-1
Shock •••••.•••••••••••••••••.•••••••••••••••.••.••...••.••••.. 8-1
Air Quality .................................................... 8-1
Acoustical Noise ••••••••••••••••••••••••••••••••••••••••••••••• 8-2
DC Power ..................................................... 8-2
Heat Dissipation ••••••••••••••••••••••••••••••••••••••••••••••• 8-'2
Cooling
••••••••••••••••••••••••••••••••••••••••••••••••••••••• 8-2
APPLICATION NOTES ••••••••••••
General •••••••••••••••••••••
Hardware Considerations ••••••••••••••••••••••••••••••••••••••••
9-1
9-1
9-2
Encoding Techniques •••••••••••••••••••••••••••••••••••••••••••• 9-4
Single Density (FM) •••••••
Double Density (MFM) ••••••••••••••••••••••••••••••••••••••
Software Considerations ••••••••••••••••••••••••••••••••••••••••
9-4
9-4
9-4
Drive Selection ............................................ 9-4
Addressable Tracks (Segments) ••••••••••••••••••••••••••••••• 9-4
Number of Sectors •••••••.••••••••••••••••••••••••••••••••• 9-5
Stream Formatting •••••••••••••••••••••••••••••••••••••••••
9-5
I/O Buffering & Sector Interleaving ••••••••••••••••••••••••••• 9-5
Retension Pass ••••••••••••••••••••••••••••••••••••••••••••• 9-6
Formatting ................................................... .
9-6
9-6
Format Description •••••••
Data Integrity ............................................. 9-9
Format Operation •••••••••••••••••••••••••••••••••••••••••• 9-9
Access Timing •••••••••••••••••••••••••••••••••••••••••••••••• 9-12
Stream To Stream ••••••••••••••••••••••••••••••••••••••••• 9-12
Seg ment To Seg ment ••••••••••••••••••••••••••••••••••••••
Read Reposit ion ••••••••••••••••••••••••••••••••••••••••••
ii
9-12
9-14

TABLE OF CONTENTS (Continued)
APPENDIX A CONFIGURATION TABLES
•••••••••••••••••••••••••••••• A-I
A.l
A.2
A.3
A.3.1
A.3.2
A.3.3
A.3.4
Jumper Options.. • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •• A-I
Stream Selection Tables.. • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •• A-I
Serv ice Aids.. • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •• A-4
Continuous Forward/Reverse •••••••••••••••••••••••••••••••••• A-4
Stream Positioning -All Streams •• • • • • • • • • • • • • • • • • • • • • • • • • • • • •• A-4
Stream Positioning - Streams 0 & 4 •• • • • • • • • • • • • • • • • • • • • • • • • • • •• A-4
Cyclic Tape Motion.. • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •• A-4
APPENDIX B OPERATING PARAMETER CONSIDERATIONS
•••••••••••••• B-1
B.l
B.2
B.3
B.4
B.5
Time Outs .........•••.....•...........................•...... B-1
Read After Write ...••...............•............•.........•. B-1
Reinstruct Timing ••••••••••••••••••••••••••••••••••••••••••••• B-2
Sectors/Segment Counts ••••••••••••••••••••••••••••••••••••••• B-2
Stream (Drive) Selection ••••••••••••••••••••••••••••••••••••••• B-2
iii

Figure
1-1
1-2
LIST OF ILLUSTRATIONS
Page
525 FloppyTape Drive ................................................ 1-1
The Evolution of Floppy Tape •••••••••••••••••••••••••••••••••••••••••• 1-2
3-1 525
Functional Block Diagram •••••••• • ••••••••••••••••••.•••••••••• 3-2
3-2 Component Location Layout •••••••••••••••••••••••••••••••••••••••••• 3-3
3-3 Read/Write Head Assembly.. • • •• • • • •• • • • ••••••••••••••••••••••••••• 3-3
4--1
4--2
4--3
4--4-
4--5
4--6
5-1
5-2
5-3
5-4-
5-5
5-6
6-1
6-2
6-3
7-1
9-1
9-2
9-3
9-4-
9-5
9-6
9-7
9-8
9-9
9-10
9-11
525
Physical Tape Layout ••••••••••.••••••••••••••••••••••••••••••••• 4--1
525 Stream Partitioning Layout ••••••••••••••••••••••••••••••••••••••• 4--2
Stream Access Flowchart •••••••••• • ••••••••••••••••••••••••••••• 4--3
Random Seg ment Access Timing •••••••••••••••••••••••••••••••••••••• 4-4
Read Timing ........................................................ 4-5
Write Timing .................. . ................................. 4-6
525 Drive Interface
525 Drive Interface
SA4-50
SA850 ......................................... .
I/O Listing ........................................................ .
Interface Signal Driver/Receiver ••••••••••••••••••••••••••••••••••••••
Read Data Signal - FM & MFM •••••••••••••••••••••••••••••••••••••
Write Data Signal - FM & MFM ••••••••••••••••••••••••••••••••••••
525 Interface Connectors -SA450 •••••••••••••••••••••••••••••••••••••
J 1 Interface Connector Dimensions SA4-50 •••••••••••••••••••••••••••••
J1 Interface Connector Dimensions -SA850 •••••••••••••••••••••••••••••
5-1
5-2
5-3
5-4-
5-6
5-7
6-1
6-1
6-2
525 Dimensions ..................................................• • • 7-1
Typical Host
System (Block Diagram) .•.•••••••••.••...•••.••.••.•••••• 9-1
Typical Floppy Disk Host
Controller •• • •• • • • • • • ••• ••• •••• ••• •• •• • • 9-2
525
Controller Example - SA4-50 ••••••••••••••••••••••••••••••••••••••• 9-3
FM vs. MFM Recording .............................................. 9-5
IBM System 34 Format Example.. • ••••••••••••••••••••••••••••••••• 9-8
Format Flowchart.. . . . . . . . . . . . . . ................................. 9-10
Verification Pass Flowchart ••••• • ••••••••••••••••••••.•••••••••••• 9-10
Stream Format Timing ••••••••••••••••••••••••••••••••••••••••••••••
Head Positioning •••••••••••••••••••••••••••••••••••••••••••••••••
Contiguous Segment-to-Segment Timing •••••••••••••••••••••••••••••
Read Reposition Timing •••••••••.•••••••••••••••••••••••••••••••••••
iv
9-11
9-12
9-13
9-14-

SECTION 1
INTRODUCTION
1.1 SCOPE
This manual describes the electrical and
mechanical characteristics 0:tr&ipher Data
Products' 525 FloppyTape 1/4-inch
cartridge tape drive. It contains the
timing, electrical, and mechanical
specifications for the 525, which is
available with a data rate of 500 KHz with
SA450 or SA850 interface, or a 250 KHz
rate with a SA450 interface. It also
recommends the formats and circuitry
necessary to interface the 525 to a host
controller.
The information in this manual is correct at
the time of publication, but is subject to
change without notice. This information is
the exclusive property of Cipher Data
Products, Inc. and shall not be reproduced
in any manner without the written
permission of Cipher Data Products, Inc.
1.2 TERMINOLOGY
The following new or, possibly, unfamiliar
terms relate to FloppyTape technology:
Figure 1-1. 525 FloppyTape Drive
o Sector - smallest unit of addressable memory located within a segment.
o Segment -a fixed length of tape that emulates a floppy disk track. Each segment is
26.55
inches, and has the capacity (unformatted) of 20.5 kilobytes. See Figure 1-2.
o Stream -one
of six physical bit serial tracks recorded on tape. Each stream
contains 255 segments (0-254). See Figure 1-2.
o Index
Pulse -a signal sent to the host controller by the 525 to indicate the detection
of an Index Mark. An Index pulse can be used by the host controller to initialize
segment operations.
o Index Mark -a portion of a stream in which the oxide is saturated in one direction.
An Index Mark is used for the logical separation of segments. See Figure 1-2.
o Upstream -a position on
tape that is between the present location and the logical
End
of Stream (EOS). See Figure 1-2.
o Downstream -a position on
tape that is between the present location and the logical
Beginning of Stream (BOS). See Figure 1-2.
o Host Controller -
the hardware required to interface the 525 to the host computer.
1-1

0
0
PHYSICAL
BEGINNING
OF TAPE
INDEX MARKS
, /
I
J--TRKO
I
--------- TRK 0 ----
I" Becomes 26.55" of Tape Recorded at 6400 BPI -I
11M I 1SEGMENT - 20.5 K BYTES I
: 4
: -~~---------------------------------------------------.
11M ISEGMENT 111M ISEGMENT 211M I SEGMENT..... I\\ ISEGMENT 255
256 Segments become a Stream
STREAM 1
..
0 0 0
.. STREAM 2 0
STREAM 3 ...
.. STREAM 4
STREAM 5
..
0 0
..
STREAM 6 o 0
~--------- DATA AREA 600' ----------a~
Figure 1-2. The Evolution of FloppyTape
1- 2
r
1/4"
0 1
PHYSICAL END
OF TAPE

1.3 GENERAL DESCRIPTION
The Cipher 525 FloppyTape cartridge tape drive is a low cost, computer data storage
tape drive, employing the 3M DC600A or any other Cipher approved 1/4-inch cartridge
tape media. The 525 emulates the industry standard SA850 or SA450 interface and
responds to
common floppy disk drive commands. Emulation of a floppy disk drive is
accomplished by the FloppyTape's on-board Z8603 microprocessor. Data is recorded in a
bit serial manner on each one of the six streams on the tape. Streams are selected by
the host system via the four Drive Select and Side Select lines supported by the standard
SA850 or SA450 bus. The host treats each stream as a logical disk surface. Prior to any
stream access, the host system must select one of the six logical surfaces. Actual
physical stream selection is accomplished by first having the Z8603 microprocessor
interpret the Drive Select and Side Select lines, then positioning the Read/Write head on
the selected stream. Each stream has an unformatted capacity of 5.2 megabytes.
Emulation of a floppy disk track is achieved by partitioning a stream into 26-inch
segments. Segments are separated by DC saturated portions of tape referred to as Index
Marks OMs).
Stream partitioning into segments by IMs is done by the Z8603
microprocessor during a stream format operation initiated by the host system. Following
the format operation, the FloppyTape uses the IMs to generate the Index Pulse signal
seen by the host on the interface. Ilvls are also used by the FloppyTape to count the 26-
inch increments of tape, when a segment seek operation is initiated by the host system
controller. The unformatted capacity of a segment is 20.5 Kbytes (approximately twice
the capacity of an 8-inch floppy disk track). Segments are accessed by the host system
using the floppy disk protocol step and direction lines from the floppy disk controller.
1.4 FEATURES
The main features of the 525 FloppyTape include:
o Standard ANSI cartridge mounting
o Precise head stepping
o SA450 or SA850 floppy disk interfaces
o Operable with existing floppy disk controller chips
o No AC requirements
o 5-1/4-inch form factor
o High capacity storage (32 MB)
o Soft sector type floppy disk format
o Enclosed/removable media
o Low maintenance
1-3

SECTION 2
SPECIFICATIONS & RELIABILITY
2.1 TAPE SPECIFICATIONS
Tape Speed/Transfer Rate:*
Ramp Time:
Tape Speed Variation
Low Frequency:
Instantaneous:
Write
Pre-compensation:
MF M Recording Density:
Unformatted Capacity (MFM Recording)
Segment:
Stream:
Cartridge:
Recording Tracks:
Recording Method:
Interface Code
Recommended:
Available:
2.1.1 Recording Times
78 ips (500 Kbits/sec)
39 ips (250 Kbits/sec)
2.1.2 Positioning
Method:
*Transfer rate is tape drive dependent.
2-1
78 ips/SOD Kbits/sec
or
39 ips/2S0 Kbits/sec
350 ms
Less
than ±2%
Less than ±6%
200 ns @ 500 Kbits/sec
250 ns @ 250 Kbits/sec
6,400 bpi nominal
26.55 inches = 20.5 Kbytes max.
255
segments = 5.2 Iv'lbytes
6 streams = 31.3 Mbytes
6
NRZ
N\odified Frequency Modulation (MFM)
Frequency Nlodulation (FM)
0.333 sec/segment
93 sec/stream
558 sec/cartridge
0.666 sec/segment
186 sec/stream
1,116 sec/cartridge
Multi-position stepper motor

2.2 RELIASD...ITY
2.2.1 Mean Time Between Failures (MTBF)
The MTBF for a drive is defined as follows:
Power-on Hours
MTBF = Number
of Equipment Failures
Definitions
Failures caused by operator error, or an out-af-specification operation, are not counted
as failures.
Product Workload is stated in terms of a unit duty cycle, and is defined as actual tape
motion time divided by total power-on time.
Infant mortality failures which occur within the first 100 hours of power-on time after
si te installation are not considered in the MTBF calculations.
The sample size must be greater than 100 units for the purpose of MTBF calculation.
Production and design maturity improvements allow the MTBF rate'to be achieved 18
months from start of production. In the interim the actual MTBF might be lower. The
minimum MTBF for the 525 is:
Product Workload
20%
40%
60%
80%
2.2.2 Mean Time To Repair (MTTR)
MTBF (Hours)
19,250
9,625
6,416
4,813
MTTR is defined
as the time for an adequately trained and competent serviceman to
diagnose and correct a malfunction at the subassembly level.
The MTTR is expected to be 15 minutes.
2.2.3 Preventive Maintenance (PM)
The 525 requires no service call related PM. The hours of required operator PM are
related to the product workload.
2-2

Product Worklood
20%
40%
60%
80%
Hours of PM/I 00 Hours On
0.1
0.3
0.4
0.4
This preventive maintenance, at a minimum, involves cleaning the tape path, including
the recording head and the drive roller surface.
2.3 DATA INTEGRITY
Errors attributed to operator mishandling of the tape cartridge, or errors on the
cartridge which can be detected and flagged during formatting, are not included in
determi ning error rates.
2.3.1 Media
Only cartridges from Cipher approved sources may be used, such as the 3M DC600A.
Properly handled, the cartridge can be used for at least 5,000 full length passes. (BOT to
EOT and back to BOT is considered 2 passes.)
2.3.2 Recoverable Read Errors
A recoverable error (soft error) is one which may be corrected by no more than 10 re-
read attempts. Data patterns, tape position, and Read/Write head position do not affect
data error rate performance.
The recoverable read error rate for the 525 is less than I in 10
9
bits.
2.3.3 Non-Recoverable Read Errors
A non-recoverable read error (hard error) is one which cannot be corrected bYl/O re-read
attempts. The non-recoverable read error rate for the 525 is less than I in 10 bits.
2.3.4 Power Loss
Accidental loss of DC power will not result in any component failure.
2-3

SECTION 3
FUNCTIONAL CHARACTERISTICS
3.1 GENERAL DESCRIPTION
The 525 FloppyTape 1/4-inch cartridge tape drive consists of Read/Write electronics,
control logic, tape drive mechanism, head positioning mechanism, and the Read/Write
head. These components perform the following functions:
o Interpret, generate, and emulate floppy disk drive control signals
o Position
the Read/Write head on the logically selected stream
o Monitor and control tape speed
o Read and Write data
Figure 3-1 is a block diagram of the 525 FloppyTape. The host system interfaces the 525
through the control and data signal bus. The control signals are interpreted, and
appropriate action is initiated by the tape motion control logic.
Tape is
transported across the Read/Write head in both directions by a direct-drive DC
capstan motor. The built-in tachometer circuit provides feedback to the control
electronics for constant motor speed adjustment.
A photo detector senses the Beginning Of Tape (BOT), the Early Warning (EW), and the
End Of Tape (EOT) holes. The on-board microprocessor initiates subsequent control
actions.
The Write protect circuitry guards against accidental alterations of recorded data
inhibiting the Write electronics when the cartridge tumbler is in the "safe" position.
Figure 3-2 shows the physical locations of these components on the 525 chassis.
3.2 READ/WRITE &: CONTROL ELECTRONICS
The Read/Write and control electronics are located on a single Printed Circuit Board
(PCB). The PCB components include the following circuits:
o Index Detector/Generator
o Write Current Driver
o Read Amplifier and Transition Detector
o Write Protect Logic
o Logical
Drive/Stream Selection
o Tape Speed/Capstan Control
o Tape Hole Monitor
3-1

--
READ DATA
-
WRITE DATA
-
-
WRITE GATE
--
-
WR ITE PROTECT
-
STEP
..
DIRECTION
-
~
TRKtl~
INDEX
...
-
MOTOR ON
--
.
-
READY
-
DS1 ..
.
DS2 ..
~
DS3 ..
SEL
.
DS4 _
-
SIS
--
~
READ
AMP
WRITE
LOGIC
~~
CONTROL
LOGIC
--
,
INDEX
DETECT
f+-
ENABLE
MTR
DRV
~~ 4~
DIRECTION
...
HI SPEED
-
... LTH
-
... UTH
-
-
.
~~
-
HEAD
-
R:3:
~
I
EOT· BOT
1
SENSOR I
,..
~
.....
I
I
I
I
I
I
I
I
n
HEAD
-
"'OSITION
Figure 3-1. 525 Functional Block Diagram
3-2

CARRIAGE
READ/WRITE
HEAD
Figure 3-2. Component Location Layout
3.3 TAPE DRIVE MECHANISM
TAPE HOLE
MONITOR
WR ITE PROTECT/
CARTRIDGE IN
SWITCHES
The tape drive capstan is driven by a three-phase, brushless DC motor. Feedback from
the integral tachometer is utilized by the on-board microprocessor for accurate pulse-
width modulation speed control.
Precise cartridge-to-head alignment is accomplished with a "floating" cartridge carriage
assembly. Forces applied, similar to those recommended by ANSI 3.55-1977, locate the
cartridge positively against the three registration pins and the datum surfaces of the
deck plate. This configuration assures exact media positioning. A sliding contact pin
opens
the tape cartridge door to enable contact between the media and Read/Write head.
3.4 READ/WRITE HEAD POSITIONING MECHANISM
The Read/Write head is positively locked
against the media by an upward turn of the
cartridge lock lever. Stream access is
performed by a multi-position four-phase
head stepper motor. The head stepper
motor is driven by the control logic in
response to Dri ve/Side Select signals
received from the host controller.
The stepper mechanism provides an
approximate step size of one mil (0.001
inch) to position the head.
The 525 is designed
with a single element,
glass-bonded ferrite/ceramic head with
tunnel erase.
PPER MOTOR
LEAD
SCREW
... ----CyLlNDER
GRAPHITE
PISTON
READ;WRITE HEAD
Figure 3-3. Read/Write Head Assembly
3-3

SECTION 4
FUNCTIONAL DESCRIPTION
4.1 POWER SEQUENCING
The DC voltage (+5V, +12V) can be applied in any sequence. However, in order to
maintain data integrity during power-up, the Write Gate line must be held inactive, or
the cartridge lock lever must be in the open position. On a power-up sequence, or the
insertion of a new cartridge, the drive automatically performs a retension pass of the
tape, leaving the medium positioned at Stream 1, Segment~. (See Paragraph, 9.4.6)
4.2 STREAM SELECTION
Stream selection occurs as a function of the Drive and Side Select lines. These lines are
used as inputs to a decode PROM. Through the use of three jumpers (W 1, W2, W3), a
total of seven possible stream configurations can be derived. (See Stream Selection
Tables, Appendix A.)
When a new
stream is selected and the Head Load or Motor On line asserted, the tape
automatically moves to Segment 0 of that stream. If no Step pulses are received, the
tape will position on the new stream at the same segment number as on the previous
stream. Each time a new stream is selected, it is recommended that the host issue a
recalibrate command to its controller to avoid tape device/controller confusion. (See
Figures 4-1 and 4-2.)
STREAM 1
..
f
0 0 0 0
..
STREAM 2 0
STREAM 3
.,
..
STREAM 4
1/4"
STKEAM 5
..
1
0 0 0
..
STREAM 6 0 0 0
EARLY
18" 18" 18'1
WARNING
HOLE
PHYSICAL
.. I
PHYSICAL END
BEGINNING
DATA AREA 600' OF TAPE
OF TAPE i
Figure 4-1. 525 Physical Tape Layout
4-1

STREAM
INDEX MARK
(DC ERASED
AREA OF
TAPE)
SEGMENT
1M SEGMENT
1M
SEGMENT
I
.... ~I--------SEGMENT-------~
A LENGTH OF TAPE WHOSE
BIT CELL CAPACITY IS
20.5 K BYTES
SECTOR- SECTOR-
NOTE- THE SOFT SECTORING OF A SEGMENT
IS A FUNCTION OF THE HOST CONTROLLER
1M
Figure 4-2. 525 Stream Partitioning Layout
4.3 HEAD LOAD/MOTOR ON
SEGMENT
1M
SEGMENT
The Head Load line on the SA850 interface serves the same purpose as the Motor On line
on the SA450 interface. This line must be asserted in order to Write or Read data_
Following the assertion of the Head Load/Motor On line, a 400 ms nominal delay is
introduced prior to any data operation to allow the medium to reach full operating speed.
If the Head Load/Motor On line is asserted and no Step pulses are issued by the host, the
525 always repositions to the last accessed segment. If, after four seconds, accessing has
still not occurred, the host should deactivate the Head Load/Motor On line to avoid
excessive wear of the medium.
4.4 SEGMENT ACCESSING
Segment accessing requires the host controller to perform the following steps:
a. Select the desired stream
b. Activate the Head Load/Motor On line
c. Read the segment/sector address mark from the tape
d. Compare the segment/sector address read from the tape to the target
segment/sector address. If there is a mismatch, go to Step e. Otherwise go to
Step f.
e. Address mismatch: determine the direction of the target segment within the
stream and activate the Direction line accordingly. Issue Step pulses equal to
the offset difference between the actual and the target address.
With the Head Load/Motor On line still asserted and with an incoming stream
of Step pulses, the 525 responds by moving the tape in the direction selected
by the Direction line until the number of Index Marks passed is equal to the
number of Step pulses received. At this point, the host should reenter this
procedure at Step c. This process is repeated until a segment address mark
compare occurs. (See Figure 4-3.)
f. Address match: access the appropriate sector within the segment.
4-2

SELECT
DESIRED
STREAM
ACTIVATE
HEAD LOAD I
MOTOR ON
READ
ADDRESS MARK
FROM TAPE
SET
DIRECTION LINE
ISSUE
STEP PULSE
YES
HOST CONTINUES
OPERATION
Figure 4-3. Stream Access Flowchart
4-3