PX3662A_UNIVAC_1540_MAG_TAPE_UNIT PX3662A UNIVAC 1540 MAG TAPE UNIT

PX3662A_UNIVAC_1540_MAG_TAPE_UNIT PX3662A_UNIVAC_1540_MAG_TAPE_UNIT

User Manual: PX3662A_UNIVAC_1540_MAG_TAPE_UNIT

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{-SPE~V RAI\D

UNIVAC

'1540
MAGNETIC
TAPE UNIT

TECHNICAL
DESCRIPTION

Table of Contents
Title

Page

General Informatio n
Modularity

Specificat ions and Standards

Electronics

Maintenance

Tape Unit Characteristics

Power and Cooling Requirements

Magnetic T ape to Computer Characteristics

Magnetic Tape Unit -

H igh-Speed Printer Off-Line Capability

List of Tables
Table

Title

Page

Word Assembly Time (Microseconds)

Effects of Various UNIVAC Computers
Operating with the UNIVAC 1540 Magnetic T ape
Subsystem

Operation Codes

Type Symbols aDd Codes

List of Illustrations
Figure

1
2

Title

Page

UN IVAC 1540 Magnetic Tape Unit
'TVAC 1540 Magnetic Tape Units and
Computer Configuration

Dimensional Data for 1540 Basic Magnetic Tape Unit
(Air-Cooled)

Magnetic Tape Unit -

Type 1540 Magnetic Tape System (Maximum Configuration)

T ape Format

Magnetic Tape Unit -

ExlemaJ Function Word Format

Bi...octal T ape Format

Octal Tape Format

Magnetic Tape Unit -

Transm it-Extra Computer Word Format

Magnetic T ape -

Computer 1nterface

Status Word Format

Tape F ile

Printer Interface

ii i

......
..........
..

. . . . . . . . . . . .:l
~

,.........

•

Figure 1.

•

UNIVAC 1540 Mtl gfl etic Tape Unit

GENERAL
INFORMATION
The militarized UNIVAC~540 Magnetic Tape Unit
(sec Figure I) provides a large capacity auxiliary
storage for computing S~'Slems o perating under severe
environment al conditions. UNIVAC tape system
engineers. through their cJl:perience in designing shipboard and land-based equ ipment to meet mili tary
system requirements. ha,-e designed and built a rugged, reliable and resjXInsi\'c. medium-speed. digital
data magnet ic tape SIDr.lge' unit to exacting military
standards. At the same lime, this unit incorporates
improvements and ad,-ances in the state-of-the-art.
The rugged cabinet design and packaging of components permi t use of the magnetic tape unit in vans.
ships. ai r-transportable helihuts or Olher e nclosures
of com pUler equipment designed 10 "go where the
action I S .

T he UN IVAC 15' .\fagnet ic Tape Unit (MT U)
employs a pinch-roller t)-pe of tape transport and
may be operated oo-Iine under co mplete computer
program control as an input output storage device o r
with a high-speed printer for off-line printing of tape
recorded information.. A flexible format allows recording and reading of four moduli (18-, 24-, 30-,
or 36-bit compuler .-urds) and three densities. and
provides recording 0{ magnetic tapes which is compatible in all res~ with ind ustry-accepted tape
systems. Either even or odd fra me parity may be
util ized a nd for added reliability. the redundant
octal fo rmat is pro\'ided_ A Read-after-Write featu re
checks each frame for parity immediately after recording. LongilUdioal parit~ recording and checking
arc automatic. A duplexing capability is prov ided
so that IwO computers communicating with the same
magnetic tape unit rna} share its facilities under program co ntroL In this wa}. data or programs stored
on one tape are available to both computers. Further
savings in the facilities a re enha nced by the ability
of the 1540 Magnetic T at>e Unit to read information
in either the forward or backward mOlion of the tape.
Records of data may be of var iable lengths and a re
separated by ~ -inch interrecord gaps (I RG) unless
otherwise extended by suitable programming. Records ma y be lengthened if suita ble interrecord gaps
were provided in previous recordings .
The UNIVAC 1540 Magnetic Tape Unit is com-

patible with all UNIVAC Military Computers and
may be supplied with an 18-, 24-, 30-, or 36-bit
parallel input/ output interface with either of two
sets of signal levels. Compatibi lity both in tape format and computer programs with the UN IVAC 1240
Magnetic T ape Un it is provided through a manual
switch selection on the 1540 Basic Unit. This feature
gives functional characteristics that a re identical with
those of the UNIVAC 1240 Magnetic Tape subsystem and permits the use of software packages designed for earlier systems.

MODULARITY
Each UN IVAC 1540 Magnetic Tape Unit (MTU) is
designed to provide a flexible, yet expandable storage subsystem to meet varied requirements. The
Basic Unit , attached to any computer channel , conta ins the interface and logic circu itry required for a
minimum syste m as well as for a maximum configuration. The 1540 Magnetic Tape Unit consists of
from one to fo ur individual cabinets each conta ining
two pinch roller type tape handlers (see Figu re 2).
The 1540 Basic Unit co ntains two tape handlers with
associated read write electron ics and one Magnetic
Tape Control (MTC ). Each 1540 Add-On Unit contains two tape handlers and associated read/ write
electronics. Thus, the Magnetic Tape Control provides the necessary jnterface and control logic for
one com puler channel and for up 10 eight ta pe
handlers.

SPECIFICATIONS AND
STANDARDS
The UN lVAC 1540 Magnetic Tape Un it was designed to meet milita ry specifications and sta nda rds
in the foll owing respects:
MIL-E-I6400, C lass 4 (0 "
Temperature:
(Centigrade)
to 50 ° operating, - 6r
to
75 " non-o perating)

Hu midity:

MIL-E-16400 (to 95 percent including condensation)

Enclosure:

MIL-STO-I08

Salt Spray:

Federal Test Method STO
151, Method 8 11

External Radiation: MIL-E- 1691O (I volt per

chassis uses wire-wrapped circuitry for improvcd
reliability.
CH .... N NEL ....

MAINTENANCE

INPur

Solid-slate, plug-in modules, along with manual control s and register and logic indicators. make maintenance of the UN IVAC 1540 fast and easy, keeping
repair time to a minimum. Manual controls permit
off-li ne maintenance of one tape unit during on-l ine
operation of other units in the system. The tape
transports and all electronics arc easily accessible
from the front of the unit. Preventive maintenance
procedurc.. and adjustments have been simplified by
several mecha nical and electrical improvements.

r~ . o

MINiMUM
CO N FIGU~4r I ON
I~ . O

MA XtMUM
CO"lfICUR4110N

CH .... NNEl B

UNIV AC
CO MP UTER

TAPE UNIT CHARACTERISTICS
Tape
Width-Y.! inch
Typc-"A" wound (oxide coating o n inside of
tape)

Fif.!,lIre 2 .

Length-3600 fect maximum
Reels- lOY.! inch , compatible hub type
Tape Ma rkers- Load Point and End of Tape
reflection markers
Method of T ape Movement- Tension Arm and
Pinch Rollers
Rea din g Method s-F orw to relain p.ogram
compotibility with UNIVAC 12.0 Ma gnetic Tape Sub.y.te m.
P.og ram . w.illen fa.
on th e UNIVAC 1.540 Magnelic Yope
Sllb,y.tem add .... only ' ape t. on.port po.ition. 1 through 8.

II.'

• =

u ro or one.

Figure 8.

External FUllction W ord Formnt

vidual tape transport is selected by bits 05-00 of the
Instruction Word. MTU consists of a maximum of
eight tape transports each of which must be assigned
a logical number by the operator on the transport
selection switch provided for eaeh tape handler.

Character Designator (Bit 8), 1 Selects Octal; 0
Selects Bi-octal
Bi-octal or octal (redundant) format is specified in
operations requiring reading or writing. The bi·octal
format disassembles 18-, 24-, 30-, or 36-bit com·
puter words into 3, 4, 5, or 6 six-bit-plus-parity tape
frames , respectively, during recording (vice versa for
reading). (See Figure 9.) The octal fo rmat disas·
scmbles 18-, 24-, 30-, or 36-bit computer words into
6, 8, 10, or 12 tape frames, respectively, during
recording (vice versa for read ing). Tape Channels
3, 4, and 5 contain the sa me information as Channels 0, 1, and 2, respeclively, in each fra me. e.xcept
when Channels 0, I, and 2 contain zeros, Channels
3, 4, and 5 contain ones. Odd parity is selected by
the Magnetic Tape Control when writing or reading
Octal Characters. The redundant recording in octal

Format (Bits 10-7)
The Format pan ion of the Instruction Word contains
Modulus, Character, a nd Pa rity designators. A com·
plete Format select ion must be included in all Inst ruction Words which request a reading or recording
operation with the exception that Modulus may be
ignored in the Write Tape Mark Instruction. The
Mod ulus designator and the Character designa tor
direct the Magnetic Tape Contra) in the assembly
and disassembly of computer words from or to tape
frames .

1'0.... ... 0 '.aPE
o ECTo()f<.;

OXIDE
SIDE

311 0 FIIAME
2ND FIIAME

• , •

FRAME

tAPE CHA.NNEl

MODULUS 3

4TH FRAME

311 0 FRAME
OXIOE
SIDE

2N D FRAM E

FRAM E

MODULUS "

StH FRAME
4TH FRA ME
OXIDE
SIDE

3RO FRAM E
2ND FRAME
1ST FRAM E

• , •

3
MODULUS

THIS EDGE
OF TAPE

TAPE CH A.N N El

}

NE x r TO

6TH FRAM E

TR AN SPO Rt

~TH FRAM E
4TH FRAME

3RD FRAM E
O KIDe
SIDE

•

·,
Figure 9.

2ND FR AME
1ST FR AME

•

TAPE CHAN NEl

MODULUS 6

Hi·octal Tape Format

format adds to the reliability (see Figure [0). For
compatible tapes, data must be recorded in Bi -octal
format.

operations, three tape frames are assembled as an
18-bit computer word for Bi-octal Character format,
or six tape frame s are assembled as an I S-bit computer word in Octa l Character format. If the computer word size is larger than [8 bi ts, the frame s are
assembled in the lower order 18 bits and zeros are
placed in remain ing high order bits (see Figures 9
and 10).

Th e Modulus Specifies tile Length of the ComlJtder
Word To Be Hecorded 011 ra pe or Read frolll tire
rape (Refer to r able 2)
Modllills 3 (designator bits 10 and 09 = 00) - An
18-bit computer word is disassembled and recorded
as three tape frames of Bi-octal Character format or
six tape frames of Octal Character format. If a computer delivers a word larger than 18 bits for recording, the Magnetic Ttlpe Control will record the lower
order 18 bits of the word on the tape and discard the
remaining high order bits. During Mod 3 reading

Modll/us 4 (designator bits 10 and 09 = 01) - A
24-bit computer word is disassembled and recorded
as four tape fr ames of Bi-octal Character format or
eight tape fram es of Octal C haracter format. If a
computer deli vers a word larger than 24 bi ts for
recording, the Magnetic Tape Control wi ll record
the lower order 24 bits of the word on the tape and
discard the remaining high order bits. During Mod

fORWARD TAPE
DIRECTION

FRAME

'"
"0

fRAME
FRAME

51' FRAME

OXID E
SIDE

2ND FRAME
1ST FR AME

, ,

•

TAPE CHANNel

MODULUS 3

''""

'51'
"
'"
"0
'"

OXIDE
SIDE

FRAME
FRAME
FR AM E
FRAME
FRAME
FRAME

2ND FRAME

, , •

FRAME

TAPE CHANNEL

M ODULUS 4

THIS EDGE

Of lAPE
NEXT TO
TRANSPORT

10TH FRAME

}
OXIDE

'"
''""
'"51'
'"

SID E

2ND FRAME

FRAME
FRAME
fRAME
FRAME
fRAME
fRAME

3RD fR AM E

, , •

IS'
0

FRAME

TAPE CHANNEl

MODULUS S
FOR WARD TAPE
DIR ECTION

12TH FRAME
11TH FR AME
10TH FR AME

'"""
'"

O XIDE
SID E

FRAME
FRAME
FRAME
FRAME

51' FRAME

'"
"0

FRAME
FRAME

2ND FRAME
I ST FRAME

, , •

MODULUS (0

Figure 10. O ctal Tape Format

TAPE CHANNEl

TABLE 2. EFFECTS Of VARIOUS UNIVAC COMPUTERS
OPERATING WITH THE UN-IVAC 1540 MAGNETIC TAPE SUBSYSTEM

MOD 3
WRITE

BCD
UNIVAC 121S

For eoch IS-bit word
received, the 1540
and 1219
Single Chonnel writes 3 fromes
(One IS-Bit
on the tope. Mod 3 is
recommended for
Word Is
Output/ Request single chonnel
operation.

MOO 5

MOD 4
WRITE

BCD

WRITE

MOD 6
WRITE

BCD

For eoch IS-bit word
received, the 1540
writes 4 fromes
on the tope: 1 frome
of zeros followed by
3 doto fromes.

For eoch 18-bit word
received, the 1540
writes 5 fromes
on the tope: 2 fromes
of zeros foJlowed by
3 do to fromes.

For eoch 18-bit word
received, the 1540
writes 6 fromes
on the tope: 3 fromes
of zeros followed by
3 doto frames.

UN IVAC 121S
and 1219
Duol Chonnel
(One 36-Sil
Word Is
Output/ Request

For each 36-bit word
received, the 1540
writes 3 frames
on the tope. Since only
the IS lSB ore written
Ihe '8 MSB are "Iosl."

for eoch 36·bit word
received, the 1540
writes 4 fromes
on the tope. Since only
the 24 Sl S are written
the 12 MSB are " 1051. "

For eoch 36-bit word
received, the 1540
writes 5 frames
on the tope. Since only
the 30 lSS are written
the 6 MSB ore "lost."
Mod 5 is commonly
used when preporing
topes for the 30-bit
computers KP-642B,
1206, or 1230).

For eoch 36-bit word
received, the 1540
writes 6 frames
on the tape. Mod 6 is
recommended for
duol chonnel
operation.

UNI VAC 1206,
1212, CP-642B,
or 1230 (One
30·Bit Word is
Output/ Request)

For each 30-bit word
received, the 1540
wri tes 3 fromes
on the tope. Since only
the 18 l SB are written
the 12 MSB ore "lost. "

For each 3D-bit word
received, the 1540
writes 4 fromes
on the tope. Since only
the 24 l SS ore written
the 6 MSB are "1051. "

far eoch 30-bit word
received, the 1540
writes 5 fro mes
on the tope. Mod 5 is
recommended for
operation with CP642B, 1206, or 1 230
Computers.

For eoch 30·bit word
received, the 1540
writes 6 fromes
on the tope: 1 frame
of zeros followed by
5 dato frames. Mod
6 is commonly used
when preparing lopes
for 36-bit computers.

l SB - least Significant Bits
MSB- Masl Significont Bits

4 read ing operat ions, four tape frames are assembled
as a 24-bit computer word for Bi-octal Character
format or eight tape frames are assembled as a 24-bit
computer word for Octal Character format. If the
computer word size is larger than 24 bits, the frame s
are assembled in the lower order 24 bits and zeros
are placed in remaini ng high order bits (see Figures
9 and 10).

as five tape frames of Bi-octal Character fo rmat or
ten tape frames of Octal Character format. If a computer delivers a word larger than 30 bits for recording, the Magnet ic Tape Control will record the lower
order 30 bit s of the word on the tape and discard the
remaining high order bits. During Mod 5 reading
operations, five tape frames are assembled as a 30bit computer word for Bi-octal Character fo rmat or
ten tape frames are assembled as a 30-bit computer
word for Octal Character format. If the computer
word size is larger than 30 bits, the frames are as-

Modulus 5 (designator bits [0 and 09 = 10) -A
30-bit computer word is disassembled and recorded

frames (read from tape) to the Magnetic T ape Control. IJari ty. even or odd. as specified in the Format
is checked fo r cach frame of the record . The six data
bits are assembled into 18 -. 24-, 30-, or 36-bit computer words according to the Modulus and Character
designator of the Format. TIle assembled computer
word is placed on the data lines of the compu ter input cable and the Input Request ( IR) line is set. The
computer samples the data lines at its convenie nce
and sets the Input Acknowledge line to the Magnetic
Tape Control. The tape cont inues to move a nd new
words are being assembled unti l the End of Record
( Interreeord Gap) is reached. The computer must
sample the input lines a nd acknowledge e;:lch IR
within a specified lime (governed by Density, Cha racter, and Modulus-Table I) (0 prevent loss of one
or more words in the record. If the com puter fails to
sample the input lines a nd ac knowledge the IR wit hin the allotted lime during any type of Read O peration. an Input Timing Error will occu r and the
Magnetic Tape Control will cease to tra nsfer data to
the computer for Ihe remainder of the record. Following the detection of the End of Record, the Magnetic Tape Control will set an Input T iming Error
Status Word on the input lines and interrupt the
computer program by setting the External Interrupt
(E I) line on that channel. When the computer
acknowledges the Interrupt, the MTU becomes
R EADY.

sembled in the lower order 30 bits and zeros aTC
placed in remaining high order bits (see Figures 9
lmd 10).

.\lodll/lls 6 (designator bils 10 and 09 = 11) - A
36·bil computer word is disassembled and recorded
as six tape frames of Bi-OClal Character format or
twelve tape frames of Octal Character formal. During Mod 6 reading operations. six tape frames are
assembled as a 36-bil computer word for Bi-octal
Character format or twelve tape frames 3Te assembled as a 36-bit computer word for Octal Character
format. (See Figures 9 and 10.)
Porit y Desigll(ltor (Bit 7), 1 Selects Odd; 0 Selects
Even
Eithe r Odd (the tota l number of ones in a frame is
odd) or Even (the lotal number of ones in a fram e is
even) Lateral Parity may be speci fied in the Instruction Word for Bi-octal Characte r writ ing and reading operations; however, Odd Parity is selected by
the Magnetic Tape Cont rol for the Octal Cha racter
writing a nd read ing operations. For compatible
tapes, Odd Parity is chosen for Bina ry data coded
and Even Pa rity is chosen for Binary Coded Decimal
(BCD) data.

Density Designator (Bits 6 and 5)
()() selects 200 !.Pi; 10 selects 556 fpi; 01 selects 800
fpi; amI '11 se ects same density as last instruction
At low density, data are recorded at 200 frames per
inc h, at medium density 555.5 frames per inch, and
at high density 800 frames per inch. Density must be
specified in Inst ruction Words requesting reading or
writing operat ions. Refer to T able 1 for word assembly a nd disassembly time.

In all types of Read Operations. Format and Dcnsi ty
selections must be made in each instruction.
Read-Forward
The selected transpon will read one record accordi ng
to the Format stated and check each frame for
parity. If a parity error is detected, the Magnetic
Tape Control will continue to transfc r data to the
computer for the remainder of th at record. After
sensing the End of Record, the Magnetic Tape Control will send a Status Word to the computer with a
signal on the External Interrupt line. This Status
Word will contain MTU status and any or all error
indica tions encountered during the read ing of the
record.

Operation Code
The Opera tion Code is located in Bits 15-11 of the
Inst ruction Word . Legal operation codes exist fo r
the six basic operations and for combinations of
these operations. The six basic operations a rc Duplex
Selection, Read, Search, Write, Space File, and Rewind , Operation Codes using any basic operation
(except Rewind) must be supplemented by Format
and Density codes placed in bits 10-07 and bits 06
a nd 05 respectively, of the Instruction Word. T able
3 is a listing of the Operation codes and Figure 8
shows the structure of the elllire instruction word.
Read OperatioWl
The selected tra nsport moves tape at 120 inches per
second in either direction a nd transfers seven-bit

Read·Backward
The selected transport will read one record backwa rd to the next Intcrrccord Oap (back one record)
according to Format a nd Density stated in the Instruction Word. Lateral and longitudinal parity will

TABLE 3. OPERATION CODES

OPERATION
CODE

00000
00001
00010
000 11
00100
00101
00110
00111

0 1000
0100 1
01010
01011
01100
0110 1
0 11 10
0111 1

10000
10001
10010
10011
10 100
10101
10 110
10111

11000
1100 1
11010
1101 1
11100
111 0 1
111 10
11111

OPERATI ON

Read (Read Forward)
Read: Selective (Selective Read-Forward)
Read: Modified Stop
Space File
Search Type I
Se a rch Type II
Se arch File Type I
Search File Type II
Write
W rite
Wr ite
Write
Wr ite
Wri te
Write
Write

XIRG
Ig nore Error Holt
XIRG, IgnQre Error Halt
Modified Stop
Edit
Tape Mark
Tape Mark, XIRG

Backread (Read Bockward)
Bochead Selective (Selective Read-Backward)
Bochead Modified Stop
Backspace Fi le
Backsearch Type I
Backsearch Type II
Backsearch File Type I
Backsearch Fi le Type II
Rewind
Rewind, Clear Write Enable
Rewind
Rewind, Clear Write Enable
Rewind-Read
Rewind -Read , Clear Write Enable
Rewind·Read
Request Tronsport·Status

Bits 17, 16 a nd 6 = 1,

a and

I, respectively, Transmi t Extra

Read-Modified Stop

be checked while reading. If a n error is detected
during backward motion, the read ing operation will
continue a nd the Status Word , upon detection of
Intcrrecord Gap, will conta in the MTU status and
the error indica tion. Cha racters wi ll be assembled in
each computer word in the same position as in a
forward read . Compu ter words, however, will be
transm itted in reverse orde r.

The selecled tra nsport will read one record accord·
ing to the Format stated and will check each fra me
for parity. A t the completion of tbe read , the magnetic tape will be stopped farther in the IRG . The
Status Word sent to the computer after detection of
End of Record will contain MTU status and any or
all crror indications including parity error.

Selective Read-Forll;ard/Backwarcl
The selected transport will read one record according to the Format stated and check each frame for
parity. Words are read and assembled as in a ReadForward/ Backward. A Selective Read Code, contained in the least significant six bits (05-00) of a
computer word. is sent by a single word output buffer to the tape unit before it can read and assemble
one word. Should this word be formed before the
Selective Read Code is transmitted, an Output Timing Error is detected. The Magnetic Tape Control
wi ll compare the least significant six bits (05-00) of
each assembled computer word with the Selective
Read Code. If the comparison is negat ive, the word
will be discarded and the reading cominued. A positive comparison causes the word to be transmitted
to the computer. However. if a parity error is detected in either case, (urther transfer of data ceases
for the remainder of the record. The Staus Word
sent to the computer after detection of End of Record will contain Magnetic Tape Unit status and any
or all error indications.

sity (refer to Table I). When the computer does not
respond within the allotted time, the End of Write is
assumed by the Magnetic Tape Control. Longitudinal parity is written and the recording process is
terminated. Tape motion is stopped after a portion
of the !nterrecord Gap is written on the tape. T he
Magnetic Tape Control removes the Output Request
and places a Status Word, indicating successful completion of the Write, on the input lines and sets the
External Interrupt line. When the compu ter acknowledges the Interrupt. the Magnetic T ape Subsystem becomes I OLE. If the computer acknowledges
the Output Request after the allotted time but before
the interrupt is sent, the Magnetic Tape Control
interprets the action as an Output Timing Error and
notifies the computer in the Status Word .

Write
The selected transpon will write on the tape according to the Format and Density stated in the Function
Word. If no recording error is detected the normal
operation continues until the computer no longer
transfers data, at which time longitudinal parity is
written and the Status Word with Interrupt is sent
to the computer.

Write Operation - Generollnfonnatiorl
When the Magnetic Tape Control senses a WRITE
function, the selected transport moves the tape fo rward and records the lnterrccord Gap.· A signal is
placed on the computer Output Request (O R) li ne.
The computer, at its convenience, responds with a
word on the data lines and places a signal on the
channel Output Acknowledge (OA) line. The Magnetic Tape Control recognizes the OA , samples the
da ta lines, and remo\'es the Output Request. The
word is transferred to the disassembly register and
another Output Request is issued. The Magnetic
Tape Control disassembles each word according to
the modulus selected in the Write Function Word,
generates frame parilY, and transfers the seven bits
to the transport for recording on tape according to
the density selected. As the recording frame passes
over the read head it is checked for parity. If a parity
error is detected, the Magnetic Tape Control stops
the Write operation and the tape motion. A Status
Word, indicating an error in recording, is placed on
the channel input lines with a signal on the Externa l
Interrupt line. If no error occurs during recording,
the process continues until the computer no longer
acknowledges the Output Request within the time
alloued for another word to be disassembled and
wriuen. This time is dependent on Format and Den-

Write·/gnore Error Halt
The selected transport will write on the tape according to the Format and Density stated in the Function
Word, but the Magnetic Tape Control will not stop
the writing process if lateral parity errors are detected as the recorded frames pass over the read
head. The Status Word sent to the computer with
Interrupt after completion will contain MTU Status
and any or all errors encountered.
Write·Ert el1c1ed Interrecord Gap (X IRC)t
The selected transport will record an Extended Interrecord Gap of 31h inches instead of the normal ~
inch IRG preceding a normal Write portion of the
operation. If no data are transferred from the computer for recording. the Extended (Dterrecord Gap
will be present on the tape and an Output T iming
Error will occur. The Status Word sent to the computer after completion will contain MTU status and
any or all error indications detected as in a normal
Write operation.
Writ e Tape Mark
The selected Iransport wilt write a fixed format Tape
Mark. The Tape Mark is a special record having

-The normal lnterrecord Gap is approximalely
inch in
length and Ihe Extended Interrecord Gap is a pproximately
3M: inehes in length.

tSpecial Le ngth interreeord Gap - Under program conIrol, interrecord Gaps other than the fi;l(ed
inch and
3!/.z inch lengths may be written. Successive
or 3!/.z
inch ga ps ma y be written by issuing the appropr iate Write
functions without initiating output buffcrs al the computer.
The program must be prepared to handle the Output Timing Error that will be indicated in Ihe Inte rrupt Status
Word following each Write operation performed in th is
ma nner.

ooes in only the 0-, I~, 2~ , and 3~bit positions of the
tint frame, followed by three frames of zeros a nd one
frame of longitudinal parity. The entire record is
9in tten by the Magnetic T ape Control upon receiving the Instruction Word. Format selection can be
ignored. To be compatible with other tape systems,
the Tape Mark must be exactly as specified above.
A Status Word with Interrupt is sent to the computer
after completion of the Write Tape Mark operation.

Search (TYIJe I and Type II - Forwon// Backward)
The Search Operation combines the fea tures of Rcad
Forward/ Backward and a Search. The selected tape
transport 'will read records from the tape either forwa rd or backward and compare the first word · of
each tape record with a Search Key (Identifier Word)
which is transmitted from the computer to the MTU
by an output buffer of one word. When a compare
is affirmative, that " FIND" record is transmitted to
the computer as in a Read Forward/Backward .

Space File-Forward/Backward

Tape motion is started upon receipt of the Instruction Word. If the MTU does not receive the Sea rch
Key from the computer before it starts reading the
record, an Output T iming Error will occur. This
read ing start time may be as short as two and onehalf milliseconds. The Search operation will be ter~
minated by the Magnetic Tape Unit when this timing
error is detected by the Magnetic Tape Control. The
Status Word containing MTU status and a ny or all
error indications will be sent to the computer upon
detecting the end of the record in wh ich the e rror
occurred. When the tape motion is stopped due to
an error, the tape will be positioned in the Interrecord Gap before the record in which the e rror
occurred if the motion is backward, and after the
record if the motion is forward. A parity error can
result from a fau lty parity check on any frame of the
tape being searched.

The selected transport will move the tape in the
selected direction to the IRG (beyond the next tape
mark). The tape is properly positioned in the IRG
for reading or writ ing. Format and Density must be
stated in the Instruction Word since par ity will be
checked during the tape motion. Any error detected
and MTU status will be indicated in the Status Word
sent to the computer with Interrupt after completion.
If the tape is at Load Point at the time the Back
Space or at End of Tape at the time the Space File
instruction is given, an Improper Condition ex ists
and will be noted in the Status Word.

Rewind
The selected transport wiU rewind the tape backward
to the Load Point at rewind speed. The Status ' Word
with lnterrupt is sent to the computer after the M ag~
netic Tape Control initiates the Rewind and not at
the complet,ion of the Rewind . If the tape is at Load
Point when the instruction is received, no tape motion or Improper Condition will result, but the Status
Word will indicate Load Point. This provides a
me thod of testing for comple tion of the Rewind
operation.

The ONES (Type I) compare is a bit~by-bit "greater~
than-or-equal" compare. H the first word of the
record is greater than or equal to the Search Key
Identifier word, a " F ind" is made. A six-bit example
is shown below.
Search Key or Identifier Word
FIND; if first word is
FIND; if first word is
NO FIND; if first word is
NO FIND; if first word is

Multifunction Operations (CeMral Infonnation )
Mu ltifunction Operations consist of combinations of
basic operations of the MTU, a nd can be performed
in response to the one Instruction Word from the
computer. Examples are the Search operations which
combine the features of a Read with the ability to do
a search on the first word of records, compare these
words against an Identifie r (Search Key) Word, and
read on a "Fi nd ." O thcr Multifunction Operations
combine a Read with a Rewind operation. COll1b i na~
tions of functions such as these save on computer
instructions, and provide some capabilities that can ~
not be achieved by using the basic opera tions one
at a time.

001101
01 1101
001 101
010101
001 100

The IDENTICAL (Type II) compare is an exact
equal compare. The first word of the record must be
exactly equal to the Search Key Identifier word to
define the "FIND" record.

Searc11 File§ Forward/Backward
The Magnetic Tape Control will perform a Search
Forward/ Backward Type I or Type II as directed
by operation code, on the selected tape transport ,
until it detects a "Find " or a "Tape Mark"t . If a
§A File is defined as one or more records separated by
Tape Marks (see Figure II).

· In a forward Scan;:h, the first word encountered in each
re<:ord is the first word of the record. In a backward
$earch, the first word encountered in each record is the
last word of the record.

tA Tape Mark is a special record on a tape placed th ere
by the operation "Wnte Tape Mark." (see Figure 6).

Tape Mark is detected before a "Find;' the Search
File operation will be terminated and the Tape
Mark Status Code will be present in the Status Word
sent to the computer after detecting End of Record.

Rewind-Read-Clellr Write Ellllble
The selected transport will perform a Rewind-Clear
Write Enable and then a Normal Read of the first
record in the forward direct ion according to the
Format stated in the Instruct ion Word . A Status
Word containing MTU status and any or all errors
will be sent to the computer with Interrupt after detecting the End of Record.

Sp(lce File Forward/Backward
The Magnetic Tape Control will cause the selected
transport 10 move the tape in the specified direction
to the Interrecord Gap beyond the next Tape Mark
and will indicate Tape Mark in the Status Word sent
to the computer detecting the End of Record (see
Figure II). Space File Forward will position a tape
at A upon completion; Space File Backward will
position the tape at B.

Request Transport Status
No tape operation is performed. The MTU sends a
Status Word reflecting the status of the selected tape
transport to the computer with Interrupt. However,
when the "Not Ready" indication is obtai ned, the
remainder of the Status Word may not be valid as it
may have been derived from other handlers.

Rewind-Read
The selected transport \\; ill Rewind the tape to the
Load Point at rewind speed and then perform a
Normal Read of the first record according to the
Format and OI;:nsit} stated in the Instruction Word.
A Status Word containing MTU status and any or
all errors ....i11 be sent to the computer with Interrupt
after detecting the End of Record.

Transmit Extra (Bits 17. 16, and 6 = 1, 0, (Iud I.
respectively)
The Transmit Extra Instruction Word is sent under
program control in response to an lnterrupt indicating a Frame Count Error al the end of a Read operation. All bilS other than 17, 16, and 6 of the
Instruction Word are ignored.

Rewin d-Clear Write Ennble
The selected transport will perform a normal R ewind
of the tape to Load Point and will clear the Write
Enable. This selected transport will no longer perform a Write function without manual intervention.
The Status Interrupt will be presented upon initiation of the Rewind and not upon completion.

The Transmit E:r;:tra provides data recovery capabilities by the transmission of a single dala word
containing the extra characters of an incomplete
computer word (6 bits per character) and denoting
those character positions void of data. The extra
characters will appear in the most significant char-

rAP E FORWARD DlREc r:o "-J
FilE
I~

____________~A~____________~\

REC ORO

RECO RO

RECO RD

RECORD

TAPE

MARK
S I I\~HNG

P05!110N

POSiTrON

Figure 11.

Magnetic Tape Unit - Tape File

•

POSITION

po..o"",
erll ",irn the specified modulus.
Ea..,.
~ the ~ .. ignificant six will refer to a
clw'xttt ro;ition: in the word originating in the
\ ;nctJo: T~ Control a~~mbly register. All bits
it'1e)
the modulu\ limi\!-; will contain D's. When~tt .3 brt In ~ lea~t signific3 m character is I. the
corre.pondmg character in the assembly register is
LQr.dil:t ..... hcn a bit i~ O. the corresponding character
IS \'3Jid '>CC !-Igure 12).

ever. this would be a valid Improper Frame Count
and would be accompanied by a Longitudinal Parity
Error.

acta"

MAGNETIC TAPE UNITHIGH -SPEED PRINTER OFF - LINE
CAPABILITY
Eithe r MTU is capable of commu nicating directly
with a UN I VAC High-Speed Printer for OFF-LI NE
operation. The MTU comm unicates with the High.
Speed Printer Unit in the Rcquest·Acknowlcdge

In the redundant format. the lack of o ne frame (char-

acter! .... auld nOI allow the last fnunc to enter the
a ....embly rcgi~tcr a nd the frame would be lost. How[

BIOCtA( ASSEMBLED WORD

•

, ,

, ,
, , 2
w

,w ,
,

,(,I

,
,

I' ,

00 '

0
0
0
0
0

BINARY

, ,

, ,
•

3 2

0 0

00 -

0
0
0
0

0 0 0 0 0
0 0 0 0 0
0 0 0 0
0 0 0
0 o ,

INDIC.A10R

" ' "' "'ME

0
0
0
0

0 0 0
0 0 0
0 0
0

00-

0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0
0
0

L ________________L _______

, ,

MOO 5

MOO 6

MOD 5 LIMIIS

MOO 4

' - - - - - - - - - - - - - - - - - ' ' - - - - - - - MOO 4 UMIIS

,,
,

0 0 0 0 0 0
0 0 0 0 0 0
0 0
0

00 '

't'

MOO J

' - - - - - - - - -- - - -- - - - ' - - - - - - - MOO 3 LIMITS

denole. 10.1 1,0"" . Y denole • • e tond 10.1 I"".... elc. A
'·0 " in Ih . . . 1'0 /'0"'10' indicoto, d.nol ••
volid hom. 01
compule< wo,d
dolo
co"e.ponding l'O'".ion
wjlhin Ihe ",odulu. Ii .. ils.

'" ".

· Th . wo.d il ide nlOcol with .h e lost (normoll., I,on.",ill.dl wo.d
• • C. PI Ihot Ihe Zo hOI been dest,oyed. no eAI.o 1.0"',.. 0 ••
pre.enl . ond Ihe I.on.mil e xt.o
100 110 ~ Equal to or Less Than
100 111 t Left-Hond Brace
101000 • Star
101001 I
101010 ~ Equal to or Grea ter Than
101 01 1
101 100 I Ri ght-Hond Broce
101 101 v (Or)
101 110

55
56
57
60
61
62
63
64

65
66

67
70
71

72
73

7'
75
76
77

101 '1 I t
110000 0
110001 I
11 00 10 2
110011 3
110100
110 10 1 5

•

110110
11011 ,

6
7

111000 B
111001 9
111010 " And
111011

III 100

111 101
11 \ 110 _ ArrC1H Right
III 111 x Multiply Sign

The laHer fou r steps arc repeated until the complete
record is tm nsfcrrcd, at which ti me the line is
printed, the paper is advanced, and the cycle is
rei niti:lled. T he process continues until the End of
File Tape Mark is read. T he High-Speed Printer
recognizes the Tape Mark as a com mand to pos ition
the paper at Top of Form on the nex t page. T he
Inte rru pt line of the Magnetic Tape Unit being con nected to the External Function li ne of the HighSpeed Printer permits the End of Record ;l nd the
Tape Mark Codes to be se nt to the High-Speed
Pri nter :IS commands to move paper one line space
or Top of Form respectively.

quest as a command to stan the read operation;
• The MTU places a word on the data lines
and sets its In put Data Request:
• High-Speed Pri mer recognizes this Input
Data Request as an Output Acknowledge:
• High-Speed Printer samples the data li nes
and clea rs its Output Data Request:
• Magnetic Tape Unit recognizes th e clea ring
of the Output Data Request as an Input
Acknowledge.

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