Digital Equipment TK50 User manual

EK-OTKSO- TM-001
.. TK50 Tape Drive
Subsystem
Technical Manual

EK-OTKSO- TM-001
TK50 Tape Drive
Subsystem
Technical Manual
Prepared by Educational Services
of
Digital Equipment Corporation

1st Edition, July 1985
Copyright 0 1985 by Digital Equipment Corporation.
All Rights Reserved.
Printed in U.S.A.
The reproduction of this material, in part or whole, is strictly
prohibited. For copy information, contact the Educational Services
Department, Digital Equipment Corporation, Maynard, Massachusetts
01754.
The information in this document is subject to change without
notice. Digital Equipment Corporation assumes no responsibility
for any errors that may appear in this document.
CompacTape is a shared trademark of Digital Equipment Corporation
and Minnesota Mining and Manufacturing Company.
The
following are trademarks of Digital Equipment Corporation,
Maynard, Massachusetts.
DEC
DECmate
DECnet
DECUS
DECwriter
DIGITAL
LA
MASS BUS
PDP
P/OS
Professional
Rainbow
RSTS
RSX
UNIBUS
VAX
VMS
VT
Work Processor

CONTENTS
CHAPTER 1 INTRODUCTION AND SPECIFICATIONS
1.1
1.2
1.3
Gene r a 1 ••••••••••••••••••••••••••••••••••••••••
TK50 Tape Drive Unit Specifications ~ •••••••••••
Drive to Controller Interface Specifications
CHAPTER 2 DRIVE UNIT THEORY OF OPERATION
2.1
2.2
2.2.1
2.2.2
2.3
2.4
2.5
2.5.1
2.5.2
2.6
2.6.1
2.6.2
2.6.3
2.7
2.7.1
2.7.2
2.7.3
2.7.4
2.7.4.1
2.7.4.2
2.7.4.3
2.7.5
2.7.6
2.7.7
2.7.8
2.7.9
2.7.10
2.7.11
2.7.12
2.7.13
2.7.14
2.7.15
General ••••••••••••••••
Uni t Des igna tions ••••••••••
Drive Unit Variations
M7546 Controller
· ..
· ...
· ...
·.
. ...
...
Cabling ••••••••••••.
Power •••••••••••••
.........
Physical Description
Drive Board •••••••
Tape Transport •••••
Controls and Indicators
Load Procedures
Unload Procedures
Lights •••••••••••
Drive Board Description
Write Data Chain
..
..
... ·.
·.
Wri te Erase ••••••••••
Write Head Selection
DC Low Circuit
........
+12 Volt Path
+5 Volt Path
Low Voltage Effect ••••
DAC Reference Voltage Generation Circuit
Automatic Gain Control Circuit
Read Head Select Circuitry ••••••
Read Amplifier Circuit •••••
Phase Lock Loop Circuit ••.•••
Pump Down Circuit
Pump Up Circui t ••••• • ••••••
VCO Gene ra ti on ••••••• • ••••
Pump Up and Pump Down Signal Generation
Data Detection •.•••.••••• • ••••
· ..
...
....
·..
Drive Commands and Status ••
...
iii
1-1
1-2
1-2
2-1
2-1
2-1
2-2
2-3
2-4
2-4
2-5
2-6
2-6
2-7
2-8
2-9
2-10
2-10
2-11
2-11
2-12
2-12
2-12
2-13
2-13
2-14
2-14
2-15
2-16
2-16
2-17
2-17
2-18
2-19
2-19

2.8
2.9
2.10
2.11
2.12
2.13
2.14
2.15
2.16
2.17
2.18
2.19
2.19.1
2.19.2
2.19.2.1
2.19.2.2
2.20
2.21
2.21.1
2.21.1.1
2.21.1.2
2.21.1.3
2.21.1.4
2.21.1.5
2.21.2
Tape Hub •••••••••••••••••••••••••••••••••••••••
Link Arms ••••••••••••••••••••••••••••••••••••
Tape Cartridge Insertion •••••• • ••••••••••
Tape Load to Beginning of Tape •••••• • •••••
Tape Motion 11 ................................... .
Read/Wri te Head ••••••••••••••••••••••••••••••
Initialization: Writing and Reading CALTRACKS ••
Wr i t i ng Da ta ••••••••••••••••••••••••• ••••••••••
Differential Signal Pair Description •••••••••••
Signal Interface Timing •••••••••••••••••••• ••
Serial Controller to Drive Communications
Basic Controller/Drive Communications Protocol
Contro11er-to-Drive Command Protocol •••••
Drive-to-Contro1ler Status Protocol •••
Change of Dri ve Sta te •••••••••••••••••
Dri ve De tec ted Errors • • • • • • • • •••
TK50 Commands ••••••••••• • • • • •••••••••••
TK50 Drive States ••••• ••••• ••••
Drive State Status ••• ••••• • ••
Done •••••••••••• • • • • ••••
Enable Write Gate •••••••••
Dropou t Sensed ••••••••••••
Track Boundary..... • ••••
Load/Run State Change •••••••
Drive Error Status ••••••••••••
............
.......
..
CHAPTER 3 DRIVE UNIT REPAIR
3.1
3.2
3.2.1
3.2.2
3.2.3
3.2.4
3.2.5
3.2.6
3.2.7
3.2.8
3.2.9
3.2.10
3.2.11
3.2.12
3.2.13
3.2.14
3.2.15
3.2.16
3.2.17
3.2.18
3.2.19
3.2.20
3.2.21
3.2.22
General ••••••••••••••••••••••••••••••••
Err 0 r C od e s ••••••••••••••••••••••••••••
Failure to Load to Beginning of Tape •••••••••
Failure to Load Tape into Cartridge ••••••••••
General Motor or Tachometer Failure ••••••
Motor A Failure ••••••••••••••••••••••••••
Motor B Failure ••••••••••••••••••••••••••
Drive Lost Control of Tape or Bad Tachometer
Excessive Drag in Tape Transport •••••••••••••
Failure to Stop Tape or Remain Stopped
Cartridge Insert Error ••••••••• ........
Cartridge Extract Error ••••• .... ...
Move ErrQr •••••••••••••••••••• .........
Deceleration Error ••••••••
Ree 1 Error ••••••••
..... ....
.....
Check Byte Error •••••••.•
Unload Error ••••••••••••••••••
8155 Memory Error ••••••••••••• ••• • ••
8155 Timer Error •••••• • ••••••••••••
Read Head 1 Error • • • • • • • • • • • • • • • ••••••
Read Head 2 Error • • • • • • • • • • • • • • • • • • ••
Cartridge Insert/Extract Error ••••• • ••
EOT Sensed in Read/Write/Seek State •••
BOT Sensed in Read/Write/Seek State ••••
iv
2-20
2-20
2-20
2-20
2-21
2-21
2-21
2-23
2-26
2-26
2-29
2-29
2-30
2-30
2-30
2-30
2-31
2-32
2-32
2-33
2-33
2-33
2-33
2-33
2-34
3-1
3-1
3-1
3-2
3-2
3-3
3-3
3-3
3-4
3-4
3-5
3-5
3-6
3-6
3-6
3-7
3-7
3-7
3-8
3-8
3-8
3-9
3-9
3-10

3.2.23
3.2.24
3.2.25
3.2.26
3.2.27
3.2.28
3.2.29
3.2.30
3.2.31
3.2.32
3.2.33
3.2.34
3.2.35
3.2.36
3.2.37
3.2.38
3.2.39
3.2.40
3.2.41
3.2.42
3.3
3.3.1
3.3.2
3.3.3
3.3.4
3.3.5
3.3 .6
3.3.7
3.3.8
3.3.9
3.3.10
Address
Address
Overflow Error
Underflow Error
Servo Error ••••••••
Failure in Tracking •••••
Command Error
Illegal Command
Write Lock Error
Write Gate Signal Timing Error
No Write Gate Error •••••
Error Sensing CALTRACKI
Error Sensing CALTRACK2
CALTRACKI Error ••••••••
CALTRACK2 Error •••••••
CALTRACK2 Offset Error
Tape Edge Error ••••••••
Top Tape Edge Tolerance Error
Drive is Overheating
BOT Sensor Error ••••••
No Hall Switch Signals
No Tachometer Pulses Present
.....
Subassembly Remove/Replace Procedures
Drive Board Removal ••••••••••••••••
Front Bezel Removal ••••••••••••••••
Read/Write Head Bracket Assembly Removal
Tachometer Removal •••••••••••••••
Solenoid/Interposer Removal
Take-up Motor Removal
Stepper Motor Removal
Heat Sensor Removal
.....
Supply Motor Removal ••••••
Receiver Assembly Removal
CHAPTER 4 TQK50 CONTROLLER THEORY OF OPERATION
4.1
4.2
4.2.1
4.2.2
4.2.3
4.2.4
4.2.5
4.2.5.1
4.2.5.2
4.2.5.3
4.2.6
4.2.6.1
4.2.6.2
4.3
4.3.1
4.3.2
4.3.3
Gene r a 1 ••••••••••••••••.
The 80186 Microprocessor
Power-up Reset •••••••••
Microprocessor Cycle Time
Memory Chip Select Lines
Peripheral Chip Select Lines
In te rrup ts ••••••••
MPSC Interrupts
FPLS Interrupts
Non-Maskable Interrupt
DMA Operations •••••
DMA Write
DMA Read
Memory
EPROM
Data
RAM
Transceivers
v
...
....
3-10
3-11
3-11
3-11
3-12
3-12
3-12
3-13
3-13
3-14
3-14
3-15
3-15
3-16
3-16
3-17
3-17
3-17
3-18
3-18
3-19
3-19
3-19
3-20
3-20
3-21
3-21
3-22
3-22
3-23
3-23
4-1
4-3
4-3
4-4
4-4
4-5
4-6
4-6
4-6
4-7
4-7
4-7
4-7
4-7
4-7
4-8
4-9

4.4
4.4.1
4.4.1.1
4.4.1.2
4.4.1.3
4.4.1.4
4.4.1.5
4.4.1.6
4.4.1.7
4.4.1.8
4.4.2
4.4.2.1
4.4.2.2
4.4.2.3
4.4.2.4
4.4.2.5
4.4.2.6
4.4.2.7
4.4.2.8
4.4.2.9
4.4.3
4.4.4
4.4.5
4.4.6
4.4.7
4.4.8
4.4.9
4.5
4.5.1
4.5.1.1
4.5.1.2
4.5.1.3
4.5.2
4.5.3
4.5.4
4.5.5
4.5.5.1
4.5.5.2
4.5.6
4.6
4.6.1
4.6.2
4.7
4.7.1
4.7.2
4.7.3
4.7.4
Control and Status Register ••••••••••••••••••••
Miscellaneous Control Register •••••••••••••••
Dri ve Erase •••••• • • • • • • • • • • • • • • • • • • • • ••
Drive Write Gate •••••••••••••••••••••••••••
Enable Gap Detect ••••••••••••••••••••••••••
Clear SA Initialization ••••••••••••••••
Clear IP Initialization •••••••••••••••••
Di ag nos tic Mode ••••••••• • •••••
Reset LED 1 • ••• •••••••• •••• • ••••••••
Rese t LED 2 •••••••••••••••••• • ••••••••••
Unit Number and Status Register ••••••••••••
SA Write Initialization •••••• . •••••••
IP Read Initialization ••••••• • ••
Drive Erase.................. • ••••
Drive Write Gate ••••••••••••••••••
Q-bus Interrupt Request •••••••••
Q-bus Interrupt Request Done ••••
Q-bus Memory Parity Error ••••••••••••••
Drive Cable In •••••••
Unit Number ••••••••••••••••
..
Vector Register • • • • ••••••
Hardware Revision Register ••• ~
SA Register •••••••.••••••••••• • •••
I P Reg i s te r ••••••••••••••••••• • •••••••••••
Module Starting Addresses/Interrupt Vectors
Unit Number DIP Switch •••••••••••••••••
Revision Level Switch Pack ••••.
Q22 Bus Interface Logic ••••••••••••
FPLS Control Logic ••• ••••••••••• • •••••
Bus Mastership Acquisition Phase •••
Data Transfer Phase ••••••••••••••••••••••••
Bus Mastership Relinquish Phase
Error During Q-bus DMA Transfer •••
FPLS Interrupt •••••••••••••••••
Q22 Bu s Reg is te r •••••••••••••••
....
....
DMA Address and Data Registers •••
DMA Address Register •••••••••
DMA Data Register ••••••••••
Q-bus Interrupt Logic ••••• • •••••••
Tape Dri ve Interface •••••••••••••••••
7201 Multi Protocol Serial Controller
Differential Drivers and Receivers
Diagnostic Hardware ••••• "........ • ••
Diagnostic Indicators •••••••••• • ••
Miscellaneous Register Loopback •••
.....
7201 MPSC Diagnostic Loopback •• •• • •••
Soft Grounds ••••.•••••••••••••••••••••
vi
4-9
4-9
4-10
4-10
4-10
4-11
4-11
4-11
4-12
4-12
4-12
4-12
4-12
4-13
4-13
4-13
4-13
4-13
4-13
4-13
4-13
4-14
4-14
4-16
4-16
4-20
4-20
4-21
4-21
4-22
4-23
4-24
4-24
4-24
4-25
4-26
4-26
4-26
4-26
4-27
4-27
4-29
4-30
4-30
4-30
4-31
4-32

APPENDIX A TQKSO DETAILED BLOCK DIAGRAM, TKSO EXPLODED VIEW
APPENDIX B
TKSO SUBSYSTEM ERROR CODES AND STATUS
INDEX
FIGURES
2-1
2-2
2-3
2-4
2-5
2-6
2-7
2-8
2-9
2-10
2-11
4-1
4-2
4-3
A-I
A-4
TABLES
1-1
2-1
2-2
2-3
2-4
2-5
2-6
2-7
4-1
4-2
4-3
4-4
4-5
4-6
B-1
B-2
B-3
8-4
B-5
B-6
B-7
B-8
System Integrated TKSO •••••••••••••••••••••••••
Desktop TK50 •••••••••••••••••••••••••••••••••••
Block Diagram: Drive Board •••••••••••••••••••••
TK50 Tape Drive Transport ••••••••••••••••••••••
TK50 Front View ••••••••••••••••••••••••••••••••
TK50 Rear View •••••••••••••••••••••••••••••••••
Physical Tape Configuration ••••••••••••••••••••
Recording Direction ••••••••••••••••••••••••••••
Signal Interface Timing {A-P} ••••••••••••••••••
Signal Interface Timing {Q-U} ••••••••••••••••••
Frame Format of Data Coming from Controller ••••
TQK50 High Level Block Diagram ••••••••.••••••••
Q-bus Timing •••••••••••••••••••••••••••••••••••
Read Data Timing •••••••••••••••••••••••••••••••
TQK50 Detai led Block Diagram •••••••••••••••••••
TK50 Exploded View •••••••••••••••••••••••••••••
TK50 Related Documentation •••••••••••••••••••••
States of Lights •••••••••••••••••••••••••••••••
TK50 Signal Definition •••••••••••.•••••••••••••
Differential Signal Pairs ••••••••••••••••••••••
Signal Interface Timing ••••••••••••••••••••••••
TK50 Commands ••••••••••••••••••••••••••••••••••
Non-Error Drive States •••••••••••••••••••••••••
Send Status Byte Bit Assignments •••••••••••••••
Miscellaneous Control Register Bit Assignments •
Common Jumper Pack Settings ••••••••••••••••••••
Address/Vector Worksheet •••••••••••••••••••••••
Floating CSR Address Chart •••••••••••••••••••••
Unit Number Switch Pack Settings •••••••••••••••
Revision Level Switch Pack •••••••••••••••••••••
Drive Error Sub-code Values ••••••••••••••••••••
Controller Internal Status Byte ••••••••••••••••
Drive Error Code Byte ••••••••••••••••••••••••••
Recoverable Dri ve Faul ts •••••••••••••••••••••••
Unrecoverable Drive Faults •••••••••••••••••••••
Dri ve Flag s ••••••••••••••••••••••••••••••••••• ,.
U/Q Port Generic SA Error Codes ••••••••••••••••
Controller Specific SA Error Codes •••••••••••••
vii
2-3
2-4
2-5
2-6
2-7
2-11
2-23
2-24
2-27
2-27
2-29
4-3
4-23
4-28
A-3
A-4
1-3
2-9
2-25
2-26
2-28
2-31
2-32
2-33
4-10
4-17
4-18
4-19
4-20
4-21
B-1
B-2
B-2
B-3
B-4
B-4
B-5
B-6

1.1 GENERAL
CHAPTER 1
INTRODUCTION AND SPECIFICATIONS
The TK50 Tape Drive Subsystem is a mass storage device. It uses
removable 94.5M byte tape cartridges to provide backup storage
capacity and a software distribution capability for Digital's
low-end computer systems.
The subsystem consists of three components: the TK50 Tape Drive,
the TK50 Tape Drive Controller, and an interface cable that
connects the tape drive to the controller. The TK50 Subsystem may
reside entirely within· the system unit of a MicroPDP-ll or
MicroVAX (I or II); or it can be set up as an external add-on
peripheral that can be plugged into other systems, including the
PDP/II-23+. The drive unit and the controller are the only field
replaceable units (FRUs) in the subsystem.
Future updates of this manual will describe controllers used with
buses other than the Q-bus. This version contains information on
the TK50 Tape Drive and the TQK50 controller (M7546).
This manual does not contain installation or remove/replace
procedures for the two FRUs. Since the TK50 fits a 5-1/4 inch
footprint and is power-plug compatible with the RX and RD50 series
disk drives, it may reside in a variety of different systems. It
may replace the RX50 in certain configurations.
Refer to the appropriate system documentation for installation and
FRU remove/replace procedures. For example, if you are
troubleshooting a TK50 subsystem problem when the TK50 is in a
MicroPDP-ll computer, refer to your Micro-II Pocket Service Guide.
NOTE
See Chapter 4 for detailed information
about the TKSO Subsystem controller(s).
See Chapters 2 and 3 for detailed
information about the TKSO streaming
tape drive.
1-1

The storage medium is a tape cartridge containing a magnetic tape
that is 1/2 inch wide and 600 feet long. The tape cartridge is
about 4 by 4 inches square, and is labeled CompacTape.
1.2 TK50 TAPE DRIVE UNIT SPECIFICATIONS
Tape speed
Bi t densi ty
Data rate
Number of tracks
Media type
Capacity
Read/wri te gap
spacing
Recording method
Power required
75 inches per second (in/s)
6667 bits per inch (bits/s)
500 Kbits/second; 45 Kbytes/second
22
Single reel, 1/2 inch, 600 feet long
131 megabytes unformatted,
megabytes formatted
0.3 inches
94.5
MFM, bit serial data, serpentine
recording
+5 Vdc, 1.2 amps (typ),
1 .4 amps (max)
+12 Vdc, 2.0 amps (typ),
2.4 amps (max)
1.3 DRIVE TO CONTROLLER INTERFACE SPECIFICATIONS
Interface type
Connector type
Cable type
Receiver type
Driver type
Differential using RS-422 drivers
and rece i vers
26-pin flat ribbon, polarized; right
angle header; PN 12-16832-02
26-wire flat ribbon; PN 17-00034-02;
max length 10 ft
AM 26LS32, differential
AM 26LS3l, differential
1-2

Table 1-1 TK50 Related Documentation
Title
TK50-D, -R Tape Drive
Subsystem Owner's Manual
TK50 Tape Drive
Subsystem User's Guide
TK50 Tape Drive
Subsystem Illustrated
Parts Breakdown (IPB)
TK50 Tape Drive
Subsystem Field
Service Print Set
Order Number
EK-LEP05-0M
EK-OTK50-UG
EK-OTK50-IP
MP-20S4 (Dri ve
uni t) MP-20 55
(M7546 module)
1-3
Contents
Provides installation,
service, use, and
programming
information for the
desktop and
rack-mounted versions
of the TK50.
Provides information
on using the TKSO Tape
Drive. Written for
operators and
secretaries with
little or no technical
background.
Provides an exploded
view drawing of the
TK50 Tape Drive
Subsystem and a
comprehensive parts
list.
The complete set of
prints needed to
troubleshoot the TKSO
Tape Drive Subsystem
to the component
level.

2.1 GENERAL
CHAPTER 2
DRIVE UNIT
THEORY OF OPERATION
This chapter provides theory of operation information about the
TK50 Tape Drive. The controller(s) to which the drive connects is
discussed in succeeding chapters.
Use the block diagrams and mechanical drawings referenced to help
you understand the text. For troubleshooting, the Field Service
Print Set takes precedence over any block diagrams or mechanical
drawings in this book.
This chapter describes how the various components in the TK50
Drive Unit interact during operation. Following the overview
theory is more specific information including signal definition
and timing, command summary and explanation, and a discussion of
the basic drive/controller communications protocol.
Chapter 3 provides the information necessary to remove and replace
a subassembly that failed in the drive.
2.2 UNIT DESIGNATIONS
This section lists and describes the unit variations in which the
TK50 Tape Drive Subsystem is available.
2.2.1
TK50
TK50-AA
TK50-AX
TK50-D
TK50-R
Drive Unit Variations
Plain drive, ordered with no system.
Single unit in packaging with tape cartridge.
Single unit in packaging, no tape cartridge.
Desktop version of TK50 -- external drive
version.
Rackmount version of TK50 -- external drive
version.
2-1

2.2.2 M7546 Controller
TQK50-AB This variation is the controller and cable for a BA23
enclosure and an external TK50-D, -R drive, and
accommodates the MSCP Q-bus. One controller handles
one TK50 drive.
TQK50-PB
Use this kit when configuring a MicroPDP-ll or
MicroVAX system in a BA23 enclosure.
This kit is the same as the one above, except that
the controller cable accommodates a PDP-ll/23+
system.
Use this kit when configuring a PDP-ll/23+.
17-00484-01 This 2.75 meter (9 foot) host-to-external-drive
interface cable is a 50-pin subminiature male to a
50-pin "D" subminiature female shielded, molded
cable. This cable comes with the TK50-D, TK50-R
subsystem.
TQK50-AA
TQK50-BA
TQK50-BB
TQK50-CB
TQK50-RB
Controller and cable in BA23 cabinet, 30 inch cable
with BA23 specific access door.
Controller in BAl23 cabinet, 30 inch cable.
Controller in BA123 and external drive, 21 inch cable
with I/O panel insert.
Controller in cabinet mount BA23 with H3490 I/O panel
and external drive. Also, 36 inch cable with I/O
panel insert.
Controller in non-FCC compliant Q-bus enclosure with
no I/O panel, 120 inch cable with bracket to mount
I/O panel insert on cabinet rails. For Field upgrade
only.
The TK50 Tape Drive Subsystem must always be ordered in two
separate pieces: the drive unit itself and, separately, the
controller. For example, if customers own a MicroVAX I system
(BA23 enclosure) and want to add an external TK50 Subsystem, they
would order the following parts.
1. TK50-D -- Desktop, external version of drive
2. 17-00484-01 -- External drive-to-system cable.
3. TQK50-AB -- Controller and internal cable.
2-2

2.3 CABLING
In the system-integrated version of the TK50 (Figure 2-1), the
drive is connected to the controller via a 26-pin flat ribbon
cable. When the TK50 is in a tabletop or rackmount enclosure, the
configuration includes an FCC shielded cable that connects the
separate enclosure to the host system (Figure 2-2).
Figure 2-1
System Integrated TK50
2-3

GREEN----...ioI..
LED
CARTRIDGE
RELEASE
HANDLE
LOAD/UNLOAD SWITCH
AND RED LIGHT
Figure 2-2
Desktop TK50
TABLE TOP VERSION
POWER SWITCH
SHR-0306-84-B
The signal lines on these cables provide serial commands and data
sent from the controller to the drive, via differential lines.
The drive recognizes the commands and data by interpreting the
differences in voltages on the lines. The differential method
provides good noise isolation. See Table 2-2 and Sections 2.16
and 2.17 for signal definition, connector pin-outs, and timing
diagrams.
2.4 POWER
The TK50 has no internal power supply. The host system must
provide the TK50's required voltages, which are: +12 Vdc at about
2 amps and +5 Vdc at about 1 amp. The power connector is the same
as the RX and RD50 series floppy diskette drives. The drive uses
a 4-pin power plug (PN 12-18855-00), located at J7 on the drive
board, to accept power provided by the host system. If an external
TK50-D, or -R drive is used, the ac power source should be the
same as that used for the host computer.
2.5 PHYSICAL DESCRIPTION
The TK50 drive unit consists of two major components: the tape
transport and a printed circuit board attached to the bottom of
the drive. These two assemblies together are one FRU. The
controller that resides in the system backplane is the other FRU.
2-4

2.5.1
Drive Board
The drive board is connected to the bottom of the drive and has
discrete analog and digital components.
This module includes an 8751 microprocessor that interprets
commands, runs on-board diagnostics, and controls the entire drive
operation. The write and read circuits necessary to translate data
to and from the MFM format reside on this board. Also included is
an 8155 I/O and RAM chip used to sense various conditions,
including Beginning of Tape/End of Tape (BOT/EOT), Handle Switch
Open/Closed, and Load/Unload Switch Open/Closed. The circuits on
this board are detailed as they apply to a specific operation.
Figure 2-3 is a simplified block diagram of the entire drive,
including the drive board.
VCO EN NRZ RD DATA
MISC VCO
SNS
8751 +
CNTRL
RD EN
DATA
RD CLOCK
SEP
TACH
INTO
PLS-L MPU SNS
(AMPL, TRACKING)
SER CMD
SER
STATUS
EN
(ECHO)
DUAL
DAC FWD
GAP
INTI
+
-L BWD
CHAN
8155
MPU
8X256
600+ FEET
EN
RAM OF TAPE
WRT
GATE
MISC
SENSE
CNTRL
WRT/ER
EN
SERVO
TIMER
ENCODE
WRT DATA (NRZ)
WRT CLOCK
WRT
COMP
-----------~ (PAL'S)
ERASE GAP
ONE 'LS 32
ONE 'LS 31
QUAD DIFF RECVR
16 MHZ
QUAD DIFF DRVR
SH R-0212-85
Figure 2-3 Block Diagram: Drive Board
2-5
•

2.5.2
Tape Transport (Figure 2-4)
The tape drive transport encompasses the mechanical and
electromechanical components that allow the TK50 to perform its
functions; that is, to read and write data to magnetic tape.
These components include: the magnetic read/write head and its
stepper motor; the take-up reel and its motor; the tape hub (which
serves, effectively, as the supply reel when a tape cartridge is
inserted) and its reel motor; and the tachometer, which provides
feedback to the 8751 microprocessor regarding tape speed.
LEADER, TAKE-UP
EXTERNAL
SHIELD
ASSEMBLY
TACHOMETER
ASSEMBLY
BRACKET &
HEAD ASSEMBLY
TK50 DRIVE
MODULE
INSULATOR
ASSMEBLY
REEL, TAKE-UP
Figure 2-4
TK50 Tape Drive Transport
2.6 CONTROLS AND INDICATORS
BEZEL
ASSEMBLY
SH R·0213·85
On the front of the TK50 Drive is a combination Load/Unload switch
and LED indicator (Figure 2-5). When power is applied and a tape
cartridge is in place, the Load/Unload switch is used to load the
tape for operation. Loading the tape involves coupling two
leaders together (one is on the beginning of the tape and the
other is part of the drive), then bringing the tape to the
Beginning of Tape (BOT) indicator. Unloading the tape· involves
rewinding to BOT, then unbuckling the two leaders so the tape can
seat in the cartridge for removal.
2-6

Also on the front of the drive is the cartridge release lever or
handle. This handle must be raised to insert or remove a tape
cartridge, and lowered to lock the cartridge in place. The handle
must never be raised when the light is on or blinking, or when the
system power is off.
Figure 2-5
TK50 Front View
2.6.1 Load Procedures
1. When power is turned on and no cartridge is in the drive,
the red light goes on steady during initialization (about
two seconds). Then the red light goes off and the green
light comes on.
2. With the red light off and the green light on, lift the
handle.
3. Insert the cartridge. As soon as the cartridge is within
about 1/2 inch of being fully inserted, the solenoid
clicks, the red light goes on steady, and the cartridge
locks in place. The green light is off.
4 •
Lower the handle so the reel
cartridge hub. The red light
light goes on. You may lift
cartridge now, if desired.
drive engages the tape
goes off, and the green
the handle and remove the
5. Press the switch to the in position. The red light goes
on and the green goes off.
2-7