IBM 3803 User manual

GA32-0021 -1
Systems

Preface
This manual provides reference information about the IBM 3803 Model 2 Tape
Control and 3420 Models 3 - 8 Tape Units.
This manual requires no prerequisite reading; however, it is assumed the reader
has a basic knowledge of stored program computers.
Second Edition (March 197 4)
This is a major revision of, and obsoletes GA32-0021-0. Changes are periodically made to the
information herein; any such changes will be reported in subsequent revisions or Technical
Newsletters.
All specifications in this manual are nominal unless otherwise indicated.
Requests for copies of IBM publications should be made to your IBM representative or to your
local IBM Branch Office.
This manual has been prepared by the IBM General Products Division, Maintainability and
Testing, Department 26T, P. 0. Box 1900, Boulder, Colorado, 80302. A form is provided at
the back of this publication for the reader's comments. If the form has been removed,
comments may be sent to the above address.
© Copyright International Business Machines Corporation 1973, 1974

Contents
Section 1: Introduction 9
Basic Subsystem . . . 9
3420 Tape Unit . . . 9
Automatic Threading 9
IBM Easy Load Cartridge 9
Tape Transport . . . 10
Read Back Checking 10
Full-width Erasure 10
File Protection . . . 10
Rewinding . . . . . 10
3420 Models 4, 6, and 8 10
Recording Methods 11 ·
6250 BPI . . . . . . . 11
1600 BPI . . . . . . . 11
800 BPI, Nine-Track NRZI 11
Seven-Track . . . . . 11
Interblock Gaps . . . . . 11
Magnetic Tape and Reels . . 11
3803 Model 2 Tape Control 13
General Characteristics 13
Addressing . . . . . . 13
Metering . . . . . . . 13
Enable/Disable Switch . 14
Power On/ Off Sequencing 15
3803 Model 2 Features 15
Nine-Track NRZI . . 15
Seven-Track . . . . 15
Two-Channel Switch 16
Device Switch 16
2 Control Switch 17
3 Control Switch 17
4 Control Switch 17
Section 2: Commands and Instructions 21
Commands . . . 21
Burst Commands 23
Write . . . . 23
Read Forward 23
Read Backward 23
Sense . . . . 23
Sense Reserve 23
Sense Release 24
Request Track-In-Error (Request TIE) 24
Loop Write-To-Read (LWR) 24
Set Diagnose . . . . . . 24
Motion Control Commands . 24
Rewind (REW) . . . . 25
Rewind/Unload (RUN) 25
Erase Gap (ERG) . . . 25
Write Tape Mark (WTM) . 25
Backspace Block (BSB) 25
Backspace File (BSF) 26
Contents 3

Forward Space Block (FSB) 26
Forward Space File (FSF) 26
Data Security Erase (DSE) . 26
Non-Motion Control Commands 27
No-Operation (NOP) 27
Mode Set 1 (MS 1) . . . . 27
Mode Set 2 (MS 2) . . . . 27
Diagnostic Mode Set (DMS) 27
1/0 Instructions 28
Test 1/0 . . . . . . . . . 28
Halt 1/0 . . . . . . . . . 28
Section 3: Subsystem Operator Functions 29
Inserting Tape Reel in Cartridge 29
Load Procedure . . . . . . . . . 29
Unload Procedure . . . . . . . . 30
Operating Procedures After Failure 30
Tape Fails to Thread (With Cartridge) . 30
Tape Fails to Thread (Without Cartridge) 30
End of Tape Comes Off Machine Reel Hub
as Tape Loads in Columns . . . . . . . 30
Tape Unit Fails to Sense EOT Marker (Tape End Comes Off Reel) 30
Tape Threads Successfully But Fails to Load in Columns 31
Window Fails to Open After Unload Operation . . . . 31
Channel Fails to Select Tape Unit (Device Switching or
Two-Channel Switch Feature Installed) 31
3420 Indicators and Pushbuttons 32
3803 Operator's Panel . . . 33
Toggle Switches . . . . . 33
Enable/Disable Switch(es) 34
Power On/Off Procedures 34
Power Off . . . . . . . 34
Power On . . . . . . . 35
Section 4: Status and Sense Information 37
Status Byte . . . . . . . . . 37
Sense Bytes . . . . . . . . . 39
Sense Byte 0 (Unit Check) . 39
Sense Byte 1 . . . . . . . 40
Sense Byte 2 (Track In Error) 41
Sense Byte 3 (Data and Equipment Checks) 42
Sense Byte 4 . . . . . . 43
Sense Byte 5 . . . . . . . . . . . . . . 43
Sense Byte 6 (Tape Unit) . . . . . . . . 44
Sense Byte 7 (Tape Unit Ready-Drop Source) 44
Sense Byte 8 (Microprogram Detected Errors) 45
Sense Byte 9 . . . . . . . . . . . . 45
Sense Byte 10 . . . . . . . . . . . 46
Sense Byte 11 (MAL 1 ROS/MP Errors) 46
Sense Byte 12 (MAL 2 ROS/MP Errors) 47
Sense Byte 13 . . . . . . . . . . . 47
Sense Byte 13, Bits 2-7 and
Sense Byte 14 (Tape Control Identification) 47
Sense Byte 15 and 16 (Tape Unit Identification -Serial Number) 47
Sense Byte 17 (Tape Control Features) 48
Sense Byte 18 48
Sense Byte 19 48
Sense Byte 20 48
4 3803-2/3420 Subsystem Description .

Sense Byte 21 (Thread and Load Diagnostics) . . .
Sense Byte 22 (Field Replaceable Unit Identification)
Sense Byte 23 (Field Replaceable Unit Identification)
Section 5: Error Recovery Procedures
Tape Cleaner Sequence
Operator Messages . . . . . . .
Action Requirements . . . . . . . .
Terminal Action la (With Operator Option)
Terminal Action lb (Without Operator Option)
Action II (Unit Check) . . . . .
Action III (Intervention Required) . . . . .
Action IV (Bus Out Check) . . . . .
Action V (Data Check On Read or Read Backward)
Action VI (Data Check On Write and Write Tape Mark)
Action VII (Overrun, Channel Data Check Chaining Check)
Action VIII (Data Check on Control) . . . . . . . . .
Action IX (Not Capable) . . . . . . . . . . . . . .
Action X (Equipment Check, No Previous Sense Bits On)
Action XI (Data Security Erase) . . . .
Action XII (Load /Point, Program Check,
Protection Check, Incorrect Length) . .
Action XIII (Command Reject, Data Converter Check)
Action XIV (ID Burst Check on Write and Write Tape Mark)
Supplementary Information
Index
49
49
49
51
51
52
52
52
52
52
52
53
53
54
55
55
55
55
55
55
55
55
56
57
Contents 5

Figures
Figure 1. Subsystem Characteristics . . . . . .
Figure 2. 3803 Model 2 and 3420 Configurations
Figure 3. Density Feature Combinations
Figure 4. Two-Channel Switch . . . . . . . .
Figure 5. Switching Configurations (Part 1 of 2)
Figure 5. Switching Configurations (Part 2 of 2)
Figure 6. 3803-2/3420 Commands . . . .
Figure 7. Inserting Tape Reel In Cartridge
Figure 8. Load Procedure . . ..... .
Figure 9. 3420 Indicators and Pushbuttons
Figure 10. 3803 Operator's Panel .....
6 3803-2/3420 Subsystem Description
12
14
15
16
18
19
22.
29
29
32
34

Abbreviations
BCD binary coded decimal LWR
loop write to read
BOT beginning of tape meter
m
BPI bytes per inch millimeter
mm
BSB backspace block millisecond
ms
BSF backspace file
MS 1 Mode Set 1
ccw channel command word MS 2 Mode Set 2
CE
cust9mer engineer
MTE multi-track error
ChE channel end
NOP no operation
cm centimeter
NRZI non-return to zero, IBM
CPU central processing unit
csw channel status word
OS
operating system
CUE
control unit end
PE phase encoded
DMS
diagnostic mode set rewind
DSE data security erase
REW
ROS
read-only storage
EBCDIC extended binary coded
RUN rewind/unload
decimal interchange code R/W read/write
EOT
end of tape secondsec
ERG
erase gap
SIO start I/ 0 instruction
FRU field replaceable unit
Sw switch
FSB forward space block Two-Channel Switch
FSF forward space file
TCS
TI
tape indicate
hex hexadecimal TIE track in error
IBG
interblock gap
TM
tape mark
ID identification
UE
unit exception
IF interface usec microsecond
1/0
input/ output
YRC vertical redundancy check
ips inches per second
Kb kilobyte
WTM write tape mark
Kd kilodigit
Abbreviations 7

Section 1: Introduction
Basic Subsystem
3420 Tape Unit
Automatic Threading
The IBM 3803-2/3420 Magnetic Tape Subsystem consists of an IBM 3803 Model
2 Tape Control and one or more IBM 3420 Magnetic Tape Units. The 3420
Tape Units are available in six models with tape speeds of 75, 125, and 200
inches per second (190,5/317,5/508 cm/sec) for Models 3/4, 5/6, and 7/8,
respectively.
The 3803 Model 2 operates at 6250 BPI and 1600 BPI densities.
A ~803 Tape Control without any switching features controls up to eight 3420
Tape Units (1 x 8 configuration).
The 3803 command set, status responses, and basic sense data are compatible
with 2400-series tape subsystems. However, there are some minor programming
differences. For example:
1. The number of sense bytes and contents of those bytes differs from those
used by 2400-series subsystems.
2. All commands not listed in Figure 6 except Mode Set type set COMMAND
REJECT (sense byte 0, bit 0).
3. A sense command must be issued after a condition is encountered which sets
UNIT CHECK in the unit status byte.
In most instances, non-time dependent programs that operate successfully on
2400-series tape units will operate correctly on a 3803/3420 subsystem with the
appropriate features.
Information presented in this section applies to all models of the tape unit.
When the operator places a file reel or a cartridge on the reel hub and presses
LOAD-REWIND, the power window closes, the automatic reel latch secures the
file reel to the hub, and tape is threaded, loaded into the columns, and positioned
at load point without further operator action.
IBM Easy Load Cartridge
When used with a solid-flange tape reel (standard IBM 10.5 inch), the IBM Easy
Load Cartridge reduces tape handling and helps prevent contamination or
physical damage.
During a load operation, if the first threading sequence is unsuccessful, tape is
rewound into the cartridge and another attempt is made.
/
Section 1: Introduction 9

Tape Transport
Read Back Checking
Full-Width Erasure
File Protection
Rewinding
3420 Models 4, 6, and 8
A single, direct-drive capstan moves tape forward or backward. Air bearings
reduce friction and tape wear since the oxide (recording) tape surface contacts
only the read/ write head, the erase head, and the tape cleaner. Short, tapered
vacuum columns greatly reduce tape inertia when starting and stopping tape. The
tapered columns and single-drive capstan start and stop tape quickly and
smoothly.
A two-gap read/ write head allows read back checking during a write operation.
Moving forward tape passes first the write gap, then the read gap.
An erase head applies a strong magnetic field that erases the entire width of tape
during write operations. Full-width erasure prevents interchangeability problems
when tape is written on one tape unit and read on another; it also reduces the
chances of leaving extraneous bits in interblock gaps or skip areas.
During a write, write tape mark, or erase operation, the tape unit monitors the
erase head operation. On a 3420 Model 4, 6, or 8 an erase head failure drops
tape unit ready status and halts tape motion. On a 3420 Model 3, 5, or 7 an
erase head failure sets UNIT CHECK, but does not drop ready status.
A write enable ring must be present in the file reel when writing. To avoid
destroying information on tape, remove the write enable ring. A reel without the
ring is "file-protected." The FILE PROTECT indicator remains on when a reel
without a file protect ring is mounted and no writing can occur.
Tape remains in the vacuum columns during rewind operations. Rewind ends
when a photocell senses a beginning-of-tape (load point) reflective marker on
tape.
During a rewind/unload operation, tape is rewound completely onto the file reel.
The tape unit is left in unloaded status, with the tape reel latch unlocked and the
window open, allowing the operator to remove the file reel.
The 3420 Models 4, 6, and 8 have the following added capabilities and features:
• 6250 BPI capability.
• 0.3-inch IBG.
Nominal data rates of 1250, 780, or 470 Kb/sec at 6250 BPI.
• Improved access times.
• Prec:1e motion control of the media to achieve faster data access times.
6250 BPI or 6250/1600 BPI density features.
• Automatic read amplification.
New tape cleaning mechanism.
3420 Models 3, 5, and 7 can be converted to 3420 Models 4, 6, and 8.
10 3803-2/3420 Subsystem Description