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G A 3 2 0 0 2 20
tBM 341013411
Systems Magnetic
TapeSubsystems
ComponentDescription
IBnfi
First Edition (December 1972)
The information in this book is subject to significant change. Any such changes will be
published in ncw editions or technical newsletters.
Requestsfor copies of IBM publications should be marJc to your IBM representative or to the
IBM branch office serving your locality.
A form for reader's comments is at the back of the book. Address any additional comments to
Half-lnch Tape Writing, Dept. 26T, Bldg. 023, IBM Br:rulder. If the form has been removed,
c o m m e n t s m a y b e s e n t t o t h e a b < i v ea d d r e s s .
o Copyright Intcrnational Business Machines, 1973
Preface
'fhis
manual describesthe IBM 3410/3411 Magnetic Tape Subsystem,Models 1,
2, and 3. In most instances, operational descriptions are limited to the channel
and Qommand level. Operations common to all I/O devices are described in
IBM System/360 Principles of Operation, Form GA22-6821, and IBM
System/370 Principles of Operation, Form GAZZ-7OOO.
Subjects covered include keys and lights, tape handling procedures, status and
sense information, and error recovery procedures.
Audience
Systems programmers who are writing programs for magnetic tape.
Systems engineers who are planning installations using magnetic tape.
Salespersonnel.
Preface 3
Contents
Introduction to Magnetic Tape Subsystems 7
Magnetic Tape Subsystem Specifications 13
Operating Procedures l5
Tape Handling and Storage. l5
Operator's Panel l6
Power On/Oft Procedures l8
Status Information and Sense Data l8
Error RecovervProcedures 32
Figures
Figure l. IBM 3410/3411Fearure Summary 8
Figure 2. CommandByte Coding (Part I of 2) 9
Figure 2. CommandByte Coding (Part 2 of 2) . n
Figure3. IBM 3410/3411Magnetic Tape Subsystem Specificarions t3
Figure4. Operator'sPanel t6
Figure 5. Unit Statusand Sense Byte Summary l9
Figure 6. Statusand Sense Indicator (Bits) CheckingSequence 33
Contents 5
I B M 3 4 1 0 / 3 4 1 IM a g n e t i T a p eS u b s y s t e m
c
3 4 1 0/ 3 4 1 l C o m p o n e n t D e s c r i p t i o n
Introduction to Magnetic Tape Subsystems
Magnetic tape is widely used as an input,/output medium becauseit rapidly stores
large amounts of information in compact, easily handled form. Tape can be used
for storing intermediateresults and for permanent storageof large files of data.
Although the recording is permanent, any previous record is erasedduring the
write operation. This means that tape can be used again and again witln
significant savingsin recording costs.
A magnetic tape subsystemconsistsof a tape control and one or more tape units.
A tape unit is an electromechanical device that transports magnetic tape past a
read,/write head, and either records (writes) data on the tape or senses(reads)
data previously recorded on the tape. A tape control is an electronic drsvice that
controls the operation of severaltape units. 'I'he tape control selectsa specific
tape unit, establishes
the necessary conditions for an operation, provides timing
signalsand delays, and controls the transfer of data between the tape r.rnitand
host system. Status and senseinformation, which monitor the progressof an
operation, are accumulatedby the subsystemand sent to the host system upon
request.
To write on tape, the tape control sends tape-motion control commands,write
control commands,and data to the tape unit. The tape unit then moves the tape
past the read/write head and writes the data on tape. To read from tape, the
tape control sendstape-motion control commands and read control commands to
the tape unit. The tape unit then moves the tape past the read,/write head, reads
the data from the tape, and sends the data to the tape control. The tapreunit
also rewinds, spacestape, and unloads tape upon command from the tape
control.
T h e I B M 3 4 1 0 / 3 4 1 1 M a g n e t i cT a p e S u b s y s t e m o n s i s t s f o n e 3 4 1 1 M a g n e t i c
c o
T a p e U n i t a n d C o n t r o l a n d u p t o f i v e 3 4 1 0 M a g n e t i cT a p e U n i t s . T h e 3 4 l l
contains the tape control and power suppliesfor the subsystem.The 34ll
c o m p l e t e l yc o n t r o l s t h e 3 4 1 0 s . T h e t a p e u n i t p o r t i o n o f a 3 4 l 1 i s i d e n t i c a lt o
that in the 3410.
There are three models of the IBld 34lO/3411 subsystem.
The Model 1 subsystemmoves tape at 12.5 inches per second (ips) resulting in a
maximum data rate of 20,000 bytes per second. A maximum of three !t4l0s can
be included in this subsystemfor a total of four tape units.
The Model 2 subsystemmoves tape at 25 ips resulting in a maximum data rate
of 40,000 bytes per second. A maximum of five 3410s can be includeclin this
subsystemfor a total of six tape units.
The Model 3 subsystemmoves tape at 50 ips resulting in a maximum data rate
of 80,000 bytes per second. A maximum of five 3410s can be includedL this
in
subsystemfor a total of six tape units.
N o t e : I n t e r c o n n e c t e d 4 1 0 s a n d 3 4 l l s m u s t b e t h e s a m em o d e l . M o d e l s c a n n o t
3
be intermixed.
Tape units attach to the tape control via individual interface cables. This is called
a "radial attachment," and it allows a tape unit to be disconnectedfrom the tape
control without affecting other tape units of the subsystem. Each tape unit signal
connector in the tape control is associated with a unique tape unit address. When
the tape control communicateswith a tape unit, the interface signalsarr: routed
only to the selectedtape unit.
lntroduction to Magnetic Tape Subsystems
T h e 3 4 l O / 3 4 l l t a p e s u b s y s t e m a n o p e r a t ei n t h r e e d e n s i t y m o d e s ; 1 6 0 0 b p i
c
( e e ) s i n g l ed e n s i t y ,8 0 0 / 1 6 0 0 b p i d u a l d e n s i t y ( n i n e - t r a c k ) ,o r 2 O O / 5 5 6 / 8 0 0 b p i
seven-track. On the 341 I tape control single density is standard. Dual density
and seven-trackare specifiedfeatures. On the 3410 tape unit, including the tape
unit portion of the 3411, all density modes are special features. One special
feature must be ordered for each 3410; single density, dual density, or
seven-track. The features are mutually exclusive;only one can be installed on a
tape unit. Figure I summarizesthe features availableon the 3410/3411.
Subsystem Feature IBM 341 Magnetic
1 I B M 3 4 1 0M a g n e t i c
Function T a p eU n i t & C o n t r o l T a p eU n i t { l n c l u d e s
t a p eu n i t i n 3 4 1 1 )
1 6 0 0B P I Single Standard F e a t u rN o .3 2 1 1
e
9-Track only Density
1600/800 BPI Dual Feature FeatureNo.
NRZI 9-Track Density No. 9150 321rl or 3221
1600 BPI PE,/ Seven Feature Feature No.
2 0 0 / 5 5 6 , / 8 0 0B P I Track No.9160 3211 or 6550
NRZI 7-Track
Figure l. IBM 3410/3411 Feature Summary
The Single Density feature allows nine-track tape units to read or write 1600 bpi
PE. No mode set command is required for the read or write operations.
The Dual Density feature allows nine-track subsystems operate in PE mode at
to
1600 bpi or in nine-track Nnzl mode at 800 bpi . Before initiating a write
operation, the channel must first issue a Mode Set 2 command to establishthe
operating mode in the tape control. A Mode Set 2 command is not necessary for
nine-track read operations.
The Seven-Trackfeature allows subsystems with a mixture of seven- and
nine-track tape units to read and write in either seven-trackNRZI mode or
nine-track PE mode. In seven-trackNRzt mode, reading and writing are done at
200,556, or 800 bpi . Before initiating a seven-trackread or write operation, the
channel must first issue a Mode Set 1 command to establishthe operating mode
in the tape control. Tape controls with the seven-trackfeature also have the
translator and data converter installed.
When on, the translator causeseight-bit EBCDIC (Extended Binary Coded
Decimal InterchangeCode) bytes from the system to be written on tape as
six-bit BCD (Binary Coded Decimal) charactersand six-bit BCD charactersto
be read from tape and translatedto their eight-bit EBCDIC equivalent. Data
rates are not changed when using the translator, nor is there any change in tape
unit operation.
When on, the data converter causes4 six-bit characters(24 bits) to be written
on tape for every 3 eight-bit bytes received from the system. Reading
seven-tracktape with the data converter on reversesthe processby converting
the 4 six-bit tape charactersto 3 eight-bit bytes. When on, the data converter
reducesthe data transfer rate to 75oh of the operating rate with the data
converter off. Data conversioncan only be used when moving tape forward, that
is, writing or reading forward.
Note: Both the translator and data converter are turned on or off by the Mode
Set 1 command.
The subsystemis under the control of the host system which can be System/360
M o d e l s2 2 , 2 5 , 3 0 , 4 0 , a n d 5 0 o r S y s t e m / 3 7 O o d e l s 1 2 5 , 1 3 5 , 1 4 5 , 1 5 5 , a n d
M
158. The host system instructs the 3410/341 I subsystemto perform specific
tasks. The tape control receives,decodes,and executesthe instructions. To
execute a command, the tape control instructs the selectedtape unit to perform
t h c d e s i r e do o e r a t i o n .
I 3 4 1 0 / 3 4 1 1 C o m p o n e n tD e s c r i p t i o n
A Start I/O instruction from the host system initiates a tape operation. The
system also sendsone of the following commands (Figure 2.ltart 1 of 2) to
designatethe clpera{.ion subsystemis to execute:
the
Write
This command records data on tape. The parity of each byte is checked when it
is received from the channel and again after it is written (readback check). The
write command also generatesan interblock gap at the end of each data block.
In pE mode, a write command issuedwhen tape is positioned at the
beginning-of-tape(aOr), generatesa pF.identification burst and a 3-inch (76
mm) gap before data is recorded on tape.
l n N n z t m o d e , a w r i t e c o m m a n d i s s u e dw h e n t a p e i s a t B O T ,g e n e r a t e s 5 - i n c h
a
( 1 2 7 m m ) g a p b e f o r e d a t a i s r e c o r d e do n t a p e .
Commands Command Byte Hex
0 1 2 3 4 5 6 7
Write 0 0 0 0 0 0 0 1 01
Read Forward 0 0 0 0 0 0 1 0 o2
Read Backward 0 0 0 0 1 1 0 0 0c
Sense 0 0 0 0 0 1 0 0 o4
Rewind 0 0 0 0 0 1 ' r 1 ol
Rewind Unload 0 0 0 0 1 1 1 ' r OF
Erase ap
G 0 0 0 1 0 1 1 1 17
Write Tape Mark 0 0 0 1 1 1 1 1 Its
B a c k s p a c eB l o c k 0 0 1 0 0 1 1 1 27
B a c k s p a c eF i l e 0 0 1 0 1 1 1 1 2F
Forward Space Block 0 0 1 1 0 1 1 1
Forward Space File 0 0 1 1 1 1 1 1 3F
Data Security Erase r 0 0 1 0 1 1 1 9l
R e q u e s tT r a c k - l n - E r r o r 0 0 0 1 1 0 ' r 1 1B
Mode Set 1 See Part 2 of this figure.
Mode Set 2 See Part 2 of this figure
Figure 2. Command Byte Coding (Part 1 of 2)
Read Forward
This command reads data from tape as tape is moving forward. The tape unit
reads data until an interblock gap is detected. The tape control checks the parity
of each byte before it is sent to channel. When reading in PE mode, single-track
errors are corrected before the data is sent to channel.
For dual density subsystems, the mode in which the read command operatesis
determined when tape is at BOT. If the PE identification burst is detected,the
tape control and tape unit are set to read tape in 1600 bpi pr, mode. If the PE
identification burst is not detected,the tape control and tape unit are set to read
tape in 800 bpi NRzl mode. The tape unit retains the mode setting until the tape
is again at BOT.
For seven-tracksubsystemsread density is determined by a Mode Set I
command.
Introduction to Magnetic Tape Subsystems
Read Backward
This command is similar to a read forward command except that tape moves
backward.
Sense
This command transfers sense data from the subsystem to the host system. The
sensebytes are stored in the tape control and tape unit. SenseBytes 0, 1, and 2,
and bits 0 to 6 of SenseByte 3 are identical to the IBM 2400-seriesand
3420/3803 subsystems.The 34lO/34 1l subsystemusesnine sensebytes. See
"Status Information and SenseData" for further description of the status and
sensebytes.
Request Track-in-Error
This command returns the track-in-error information (SenseByte 2) from the
host system to the subsystem. The tape control uses the data to correct the next
data block read. This command is effective only when correcting single-track
read errors during nine-track NRZI operations. It is executed but not effective
during PE and seven-trackoperations.
Write Tape Mark
This command writes a special block on tape that is used to separate the files on
tape. This special block is generatedby the subsystem;no data is transferred
from channel. A readback check is performed on the tape mark. If an error is
detected,tape is repositionedand the tape mark is rewritten.
In PE mode with tape at BOT, a pE identification burst is written and a 3-inch
(76 mm) gap is generatedbefore the tape mark is written.
In NRZI mode with tape at BoT, only the S-inch (127 mm) gap precedesthe tape
mark.
Erase Gap
This command erasestape for a predetermineddistance. If tape is not at BOT,
the distance erasedis 3.6 inches (91 mm).
In PE mode with tape at BOT, the PE identification burst is written, then a 3-inch
(76 mm) gap is erased.
In NRZI mode with tape at BoT, a 5-inch (127 mm) gap is erased.
Successiveerase gap commands can be issued to generate longer gaps.
Data Security Erase
This command erases tape from the point at which it was initiated to the
end-of-tape (Eor) marker. Data Security Erase is acceptedby the subsystem
only when chained to an Erase Gap command. To erase tape beyond the EoT
marker, successiveErase Gap commands must be issued.
Rewind
This command rewinds tape to BOT. If tape is at BOT when the command is
issued,the operation is terminated immediately without error.
Rewind Unload
This command rewinds tape to BoT and then unloads tape. If tape is already at
BOT, tape is unloaded to complete the operation.
Forward Space Block
This command moves tape forward to the next interblock gap.
l0 3410/3411Component
Description
Forward Space File
This command moves tape forward to the interblock gap beyond the first tape
mark encountered.
BackspaceBlock
This command moves tape backward to the next interblock gap or to BOT,
whichever occurs first.
Backspace File
This command moves tape backward to the interblock gap beyond the first tape
mark encountered or to BOT, whichever occurs first.
Mode Set I (Seven-Track Feature)
This command establishes operating conditions in the tape control for subsequent
seven-track read or write operations. The Mode Set I command determines the
density, turns the data converter and translator on or off, and sets subsystem
operations to odd or even parity. The subsystem retains its mode setting until
reset or until it receivesanother mode set command. See Fisure 2. Part 2 of 2.
200 556 800 1600 o d d Even DC oc Translate Translate Command Byte Hex
Parity Parity On off On off 0 1 2 3 4 5 6 7
Mode Set 1 (Seven-Track)
x x x X 0 0 0 1 0 0 I 1?
X X x X 0 0 1 0 0 0 I aa
X x X X 0 0 1 0 1 0 1 1 L6
X X x X 0 0 1 1 0 0 1 1 33
X X x X 0 0 1 1 1 0 1 1 3B
x X X X 0 0 1 0 0 1 53
X x X X 0 1 0 0 0 1
x ,l
X X x 0 0 1 0 1 6B
X x X X 0 1 1 1 0 0 1 73
X X X X 0 1 1 1 I 0 1
7B
X X x X I
0 0 1 0 0 1
X x x X 1 0 0 0 0 1 A3
X X X X 1 0 0 1 0 1 AB
X X x X I
0 r 0 0 1 1
X X x x 1
0 I 1 0 1 1 utJ
Mode Set 2 (Nine-Track)
x 1 0 0 0 0 I 1 a?
x 1 0 0 1 0 I I CB
Note l: Seven-trackMode Set 1 commandsare treated as NOP-reset sensebytes when issuedto a tape controt
without the seven-trackNRzt feature.
Note 2: Nine-track Mode Set 2 commands are treated as NOP-reset sensebytes when issuedto a tape control
without the nine-track NRzl feature.
Figure 2. Command Byte Coding (Part 2 of 2)
Introduction to Magnetic Tape Subsystems 11
Mode Set 2 (Dual Density)
This commandestablishes operatingconditions(1600 bpi or 800 bpi) in the
the
tape control and tape unit for subsequent
nine-trackwrite operations.
The
commandis accepted the tape unit only when the tape unit is at BOTon a
by
write-typecommand.During read operations, mode is automatically when
the set
tape is at BoT. (See"Read Forward.")
1.2 34lO/3411 ComponentDescription
Magnetic Tape Subsystern Specifications
Characteristics Model 1 Model 2 Model 3
Tape Speed (ips) 12.5 25 S0
Write Access Time* 15 ms 12 ms 6 ms
R e a dA c c e s sT i m e * 15 ms 12 ms 6 ms
Data Rate:
1600 bpi 20 kb/sec 40 kb/sec 80 kb/sec
800 bpi 10 kb/sec 20 kb/sec 40 kb/sec
556 bpi 6.95kb/sec 13.9kb/sec 27.8kb/sec
200 bpi 2.5 kb,/sec 5.0 kb/sec t0.0 kb/sec
Time Per Byte:
1600 bpi 50 usec 2b usec 12.b usec
800 bpi 100 usec 50 usec 25 usec
556 bpi 144 usec 72 usec 36 usec
200 bpi 400 usec 200 r.rsec 100 usec
Interblock ap (lBG):
G
Length/Time
Nrne-Track 0.6 inl48 ms 0.6 inl24 ms 0.6 inl12 ms
Seven-Track 0.75 in,/60 ms 0.75 in,/30 ms 0.75 in,/15 ms
R e w i n dT i m e ( t 1 0 % ) 3 minutes 3 minutes 2 minutes
(2400 feet)
T a p eT h r e a d i n g Manual Manual Manual
R e e ls i z e s( i n c h ) 1 0 . 5 ,9 . 5 , 7 , o r 6 ( f o r a l l m o d e l s )
Tape Requirements
The following half-inchtapes can be used: IBM Series/500,IBM Heavy Duty, IBM Dynexcel@,
or competitive formulations which meet the tape and reel criteria in Tape Specifications,
Form
GA32-0006.
Note: IBM tapes other than those named above do not provideadequatereliability
and should
not be used.
* Read Access Time is the intervalfrom issuanceof a Read Forwardcommand given to the
tape control when tape is not at load point, until the first data byte is read when tape is
brought up to speed from stopped status.
* Write Access Time is the intervalfrom the issuanceof a move command to the tape unit
when tape is not at load point, until the first data byte is written on tape when tape is
brought up to speed from stopped status.
Machine Environment
RelativeHumiditv: 20 to 8O%6
Temoeratures:
O p e r a t i n g : 0 t o 9 0 " F ( 1 5 . 6t o 3 2 . 2 ' C )
6
N o n - O p e r a t i n g5 0 t o 1 1 0 " F ( 1 0 t o 4 3 . 3 ' C )
:
M a x i m u mW e t B u l b : 7 8 ' F ( 2 5 . 6 ' C )
Metric equivalents:
1600bpi : 6 3 b y t e sp e r m m 0.6 inches : 15,2mm
800 bpi = 3 1 , 5 b y t e sp e r m m 0.75 inches : 19 mm
556 bpi : 2 1 , 9 b y t e sp e r m m 6 inches = 1 5 2 , 4m m
200 bpi : 7 , 9 b y t e sp e r m m 7 inches : 1 7 7 , 8m m
50 ips : 1 2 7 0m m p e r s e c o n d 8.5 inches : 216 mm
25 ips : 635 mm per second 10.5 inches = 266,7 mm
12.5 ips : 317,5 mm per second 24OOfeet : 732 meters
Figure 3. IBM 3410/3411 Magnetic Tape Subsystem Specifications
Magnetic Tape SubsystemSpecifications 13
Operating Procedureg
This section contains procedures for handling and storing tape, turning power on
and off, and recovering from errors. Also included are descriptions of the
Operator's Panel and of the status and sense bytes. Refer to the IBM
3410/3411 Operator's Guide, Form G232-0004, for additional operating
procedures.
Tape Handling and Storage
Tape Handling
A tape reel that is not in use on a tape unit should always be stored in its
container. Establish procedures to protect magnetic tape from contamination
which causes degraded tape unit performance. Some common rules are:
1. Never leave tape reels or containers exposed. Tape may be damaged, or dust
accumulating on the tape or in the container can contaminate the tape.
2. Erasing a tape reel identification label is a cause of contamination. Use new
labels when changing reel identification. Select a label with an adhesive
backing that does not leave a residue and that can be applied and removed
easily.
3. Never allow a loose end of tape to trail on the floor; dirt picked up in this
manner can reach the tape transport and be passed on to other sections of the
tape.
4. Do not allow smoking in areas where tape is in use. Ashes contaminate tape.
Live ashes can permanently damage the tape surface.
5. Don't touch the tape edges through the reel openings or press on the reel
flanges. Such pressure will compress the tape and damage its edges.
6. Be very careful when removing the write-enable ring. Always unload tape
before removing the write-enable ring; never remove the ring while tape is
loaded on the tape unit.
Tape Storage
To prevent tape contamination and damage during storage, follow these
procedures:
1. Before a tape is stored, securethe loose end of tape with a tape end retainer
to prevent the tape from unwinding in the container.
2. Always store tape in an upright position. Never store tapes flat or in stacks;
accidental damage or reel warpage may result.
3. Store tapes in a cabinet or shelf elevated from the floor and away from
sources of paper and dust. Dust can be transferred from the outside of the
container to the reel during load and unload operations.
Operating Procedures l5
Operator's Panel
trtrtrtr
trtrEtr
Figure 4. Operator's Panel
SELECT
This lamp is turned on when the tape unit is being operated by the tape control.
The tape unit must be ready before it can execute commands from the tape
control.
READY
This lamp indicatesthat the tape unit is capable of executing commands from the
tape control.
To turn on the READY lamp, the tape unit must be loaded, the cover closed, the
STARTkey must be pressed,and tape must not be in motion (as in a load or
rewind operation for example). Pressingthe STARTkey while tape is loading or
rewinding, causesthe READY lamp to turn on after the operation is complete and
tape motion stops.
FILE PROTECT
This lamp indicatesthat the tape unit is not capable of executing a write or erase
command.
T h e F t L E P R O T E C T ' l a m ip t u r n e d o n w h e n t h e t a p e u n i t i s n o t r e a d y ,o r w h e n a
s
file-protected tape reel is mounted. A file-protected reel is one from which the
write-enable ring has been removed. The write-enable ring should be removed
from the back of the tape reel to protect information on the tape from accidental
erasureor rewrite.
TAPE INDICATE
This lamp is turned on when the end-of-tape (eclr') reflective marker is sensed
with tape moving in a forward direction. SensingEot' in write status sets unit
exception. The lamp is turned off when the EOl marker is sensedwith tape
moving in a backward direction.
RESET
Pressingthis pushbutton removes the tape unit from ready status, turns off the
READY lamp, stops tape motion, and prevents the tape unit from respondingt commands from the tape control.
l6 3 4 l O / 3 4 1 I C o m p o n e n tD e s c r i p t i o n
UNLOAD REWIND
This pushbutton causesthe tape unit to rewind tape to load point and then
unload. If the tape is at load point when UNLOAD REwtND is pressed,the tape
unit unloads immediately. The UNLOAD REwTNDpushbutton is disabled when
the tape unit is ready.
START
If the tape unit is loaded, pressingthis pushbutton allows the tape unit to
respond to commands from the tape control, turns on the READY lamp, and
disablesall other pushbuttonsexcept RF.SET.
If the tape unit is ready or not loaded, the START pushbutton has no effect.
LOAD REWIND
lf the tape unit is not loaded, pressingthis pushbutton causesthe tape to load
into the vacuum columns and to be moved forward to load point (the load point
reflective marker is sensedat the photosenseblock). The eOr reflective marker
must be positioned to the left of the vacuum columns.
If the tape unit is loaded, not ready, and tape is not positioned at load point,
pressingthis pushbutton causestape to move backward (rewind) to load point.
If the tape unit is ready or if tape is already positioned at load point, pressing
L O A D R E W I N Dh a s n o e f f e c t .
ENABI,E/DISABI,E
This switch allows the subsystemto be taken off-line for maintenance.Operation
o f t h i s s w i t c h ( l o c a t e do n t h e 3 4 1 1 ) i s i n t e r l o c k e dw i t h t h e s y s t e mp r o g r a m . T h e
switch setting can be changed at any time, but the subsystemchangesstatus only
when the system is in a Halt or Wait state. The switch must be set to the
ENAtsLEposition to put the subsystemon-line. The switch must be set to the
D I S A B L E o s i t i o nt o t a k e t h e s u b s y s t e m f f - l i n e .
p o
A clisabledsubsystemis nonexistentto the system program.
Note: When the switch is set to DISABLF., subsystemdoes not go off-line
the
until all pending status information (except a device end resulting from selecting
a not ready tape unit) is acceptedby the program.
When the subsystemis to be disabled (or enabled), proceed as follows:
L T u r n t h e E N A B L . F . / D I S A Bs w i.t c h t o t h e E N A B L E( o r D T S A B L Ep o s i t i o n .
LF )
2. PresssTOP and then sTART at the system console. The subsystemis now
on-line (or off-line).
Usage Meter
A time meter on the 34ll records the elaspedtime that the tape control is in
use. The meter runs whenever the subsystemis enabled (on-line) with the
F - N A B L E / D I S A B L E i t c h , a n d t h e h o s t s y s t e mi s o p e r a t i o n a l .
sw
A t i m e m e t e r o n e a c h 3 4 1 0 r e c o r d so n l y t h e t i m e t h a t t h e t a p e u n i t i s i n u s e .
The meter runs whenever the subsystemis enabled, tape is away from load point,
a n d t h e h o s t s y s t e mi s o p e r a t i o n a l .
Operating Procedures 17
Povner On/ Ot+ Procedures
Normal power on/off sequencing for the subsystem is controlled by the system
power interlock circuits. Maintenance activities (such as taking a tape unit
off-line) may necessitate dropping power in the tape control.
Voltage transients caused by dropping or bringing up tape control power during
system operation can causeerroneoussystem interrupts. To avoid this, use the
following procedureswhen dropping or bringing up tape control power:
Power Off Procedure
The channel to which the tape control is attached must have completed all
operations and have no pending interrupts.
L Vary the subsystemoff-line (refer to your operating system guide).
2. Set the ENABLE/DISABLE switch to DISABLE. This allows the subsystemto so
off-line when the system reachesa 'wait state.'
Optional: To force the system into a wait state, press STOPthen STARTat the
system console.
3. Turn power off at the tape control after the tape control goes off-line.
Power On Procedure
I . S E t E N A B L E / D I S A B L E W i t C hO D I S A B L E .
S t
2. Turn power on at the tape control.
3. Set the ENABT-E,/DISABLE switch to ENABLE. This allows the subsystemto go
o n - l i n e w h e n t h e s y s t e mr e a c h e s ' w a i t s t a t e . '
a
Optional: To force the system into a wait state, press STOPthen STARTat the
system console.
Status lnfornnation And Sense Data
Urrit Status Byte
The unit status byte contains eight bits of status information pertaining to the
selectedtape unit and tape control. Unit status information is retained by the
tape control or channel until it is incorporated in the channel status word (csw),
or until another operation is accepted. Unit status information is updated at the
beginning of each tape operation (except Test I/O) to indicate initial status. It is
also updated during a tape operation to provide ending status at termination of
the l/O operation. This information is set in the status portion of the channel
status word by an I/O interruption or, under certain conditions, by a Start I/O,
Test I/O or Halt I/O instruction. Bits 32-39 of the csw, which indicate tape
unit and tape control status, are describedin this section. Bits 40-47 of the CSw,
which indicate channel status, are describedin IBM System/360 Principles of
Operation. Form GA22-6821.
l8 3 4 l O / 3 4 1 I C o m p o n e n tD e s c r i p t i o n
Notes:
1. Only one channel end and device end are generatedfor each I/O operation.
2. Channel end and device end are not generated when programming errors or
equipment malfunctions are detected during initiation of an operation prior
to tape control returning its status.
3. When command chaining takes place, only the channel end and device end
of the last operation are made available to the program.
4. The channel may or may not present channel end to the operating system
even though channel end was present in the subsystemending status when
a control unit end or device end prematurely terminated a chain of
commands,or during the initiation of a chained command.
5. If an unusual condition is detected during initiation of a chained command,
the chain is terminated without the device end indication.
Serrse Data
Sensedata provides detailed information about the selectedtape unit and about
the last operation performed by the tape control. Information transferred by the
sensecommand is more detailed than that supplied by the unit status byte, and
may be used to determine the cause of a unit check indication. Fisure 5
summarizesthe status and senseinformation.
Unitt Status and Sense Byte Surrrmary
Bit 0 ,| 2 J 4 5 o 7
Byte
U n i t Attention Status Control Unil Busy C h a n n e lE n d Device End Unit Check Untt
Status ( N o t U s e d ) Modifier End Exception
Sense B
0 Command Intervention Bus Out Equipment Data Check * Overrun t Word Count Data
Reject * Required * Check * Check * Zero * Converter
Check *
I Nose t Tape Unit Tape Unit Seven-Track Load Pornt Write Status File Protected Not C a p a b l e
Status A Status B Tape Unit
2 Track i n - E r o r
r
M u l t i p l eT r a c k End Data
Read/Write Envelope 1600BPI Set
J Erroror LRC Skew Error1 C h e c ko r C R C Backward Not Used
VRC t Check t in TapeUnit
Errort t
TapeUnit
4 T a p eU n i t D i a gn o s t r c Tape Unrt
Positioning Tape Indrcate Not Used Not Used Not Used
Rejecrf Track Check t Check
C h e c kf
New New Write Tape PE lD Burst Parity F al s e E n d Reserved for
5 Tach Check f
Subsystem Subsystem M a r k C h e c k# Check* Compare t Mark t RPO
Seven-Track S h o r t G a p Alternate
6 Dual Density Tape Unit Model ldentrfrcatron
Tape Unit Mode Density
"""a""r*r ,*.
L a m p C h e c k Left Column Right Column Ready Reset
7 r Check n Check s f,
l*, Not Used Not Used
Feedthrough Readback
8 No1 Used End Velocity Start Velocity
Not Used Data not Not Used Not Used
Check Check i Check f
Detected #
t Sets Data Check
# Sets Equipment Check
* Set:; Unit Check
E Sets Taoe Unit Check
Figure 5. Unit Status and Sense Byte Summary
OperatingProcedures l9
STATUS BYTE
Bit Designation Interpretation
0 Attention Not Used
1 Status Modifier Used with bit 3 (Busy): bits I and 3 oN indicate the
tape control is busy or has an interrupt pending for a
tape unit other than the one addressed.
2 Control Unit End Control unit end indicatesthe tape control has
become available for another operation.
Control unit end is set:
l. At completion of every tape control operation
during which control unit busy was signaled.
2. At completion of a control command (which
presentedchannel end in initial status) in which a
unit check or unit exception is detected.
3 Busy Busy indicates the tape unit or tape control cannot
execute a command or instruction because one of
them is executing a previously initiated operation or
has a pending interrupt condition.
Bit 3 (Busy) oN and bit I (Status Modifier) opr
indicates:
l. That any command (including Test I/O) is
recognized, no interrupt is pending, and the
selectedtape unit is rewinding or performing a data
security erase.
2. That any command other than Test I/O is
recognizedand:
a. The tape control has a control unit end interrupt
pending.
b. The addressedtape unit has a device end or unit
check interrupt pending.
4 Channel End Channel end indicates completion of the portion of an
I/O operation involving transfer of data or control
information between the tape control and channel.
Channel end means that the channel is availablefor
another operation. Channel end is set when a read,
read backward, write, or sensecommand has been
completed, or when a control command has been
accepted by the tape control.
5 Device End Device end indicatescompletion of anl/O operation
at the tape unit, or when the tape unit is made ready
manually. Device end indicatesthat the tape unit is
availablefor another operation. Also see SenseByte
1, Bits 1 and 2 (Tape Unit Status A and B).
Device end is set:
l. When a load operation has been completed and the
STARTkey is pressed(tape unit goes from not
ready to ready status).
2. When a rewind-unload operation is completed at
the tape control level.
20 3410/3411 Component Description
3. When a control command is completed at the tape
unit level.
4. Along with channel end at the completion of other
commands.
5. Along with unit check when a tape unit that is
performing any operation except rewind unload or
rewind becomes not ready (that is power off,
manual reset, etc).
6. When a tape unit becomes not busy after selection
was attempted while the tape unit was busy.
6 Unit Check Unit check indicates the tape unit or tape control has
encountered an unusual condition. Cause of a unit
check is stored as sense data that is available to the
program in response to a sense command. Unit check
is set when any of the following occur:
1. Any bit in SenseByte 0 is set.
2. A read backward, backspace block, or backspace
file operation is initiated into or at load point.
3. A rewind unload operation becomes effective at
the tape unit level (interrupt status cycle).
4. SenseByte l, Bit 7 (not capable) is set.
5. SenseByte 5, Bit 3 (PE identification burst) is set.
6. A failure occurred which prevents completion of a
data security erase command.
7. An error occurred during a space operation after
channel end was presented.
7 Unit Exception Unit exception indicates the tape control detected a
condition that usually does not occur, but is not
necessarily an error. Unit exception is set:
1. If tape indicate is on during a write, write tape
mark, or erase gap operation.
a. Tape indicate is turned on when the tape unit
sensesthe end-of-tape (Eor) reflective marker
while tape is moving forward.
b. Subsequent write, write tape mark, or erase gap
instructions result in additional unit exception
indications if tape indicate is not reset.
c. Tape indicate is turned off when the tape unit
sensesthe EoT reflective marker while tape is
moving backward, or when tape is unloaded.
d. Sensingthe EoT reflective marker during a data
security erase operation does not set unit
exception. The data security erase operation is
completed when tape reaches the EoT reflective
marker.
Operating Procedures 2l
2. lf a tape mark block is detected during a read, read
backward, forward space block, or backspace block
operation.
Note: A 'service out' response to 'status in' clears
unit exception. Because read and space-block
operations do not set unit exception again, it is
important to handle a unit exception when it is
recognized.
22 34lO/3411 Component
Descriprion
SENSE BYTE O
Bit Designation Interpretation
0 Command Reiect Present:
l. If a write, write tape mark, or erase gap command
is issued to a file-protected tape unit.
2. If an illegal command is decoded.
3. If a data security erase command is issuedwithout
chaining it to an erase gap command.
I Intervention Presentif the addressedtape unit
Required is not ready or is nonexistent.
2 Bus Out Check Present if channel bus out has incorrect (even) parity
during a command byte or data transfer.
3 Equipment Check Present if any of the following are set:
SenseByte 4, Bits 0 or I
SenseByte 5, Bits 5 or 2
SenseByte 8, Bit 4
4 Data Check Present if any of the following are set:
SenseByte I, Bit 0
S e n s e y t e 3 , B i t sO , 1 , 2 , 3 , o r 4
B
SenseByte 4, Bit 5
SenseByte 5, Bits 4 or 6
SenseByte U, Bits 3 or 5
5 Overrun Presentwhen service is requestedbut data cannot be
transferred during a read, read backward or write
operation. Data transfer stops when overrun is
detected.
6 Word Count Zero Present:
If channel respondswith command out to the first