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The MTU9104/9105/9112/9113 Magnetic Tape
Units are compact, self-contained rackmountable
units for use on Model 33 and larger systems. A
choice from among four different tape units enables
users to select tape units best suited to their tape
processing requirements. Table 1-1 lists the speci-
fications for the various magnetic tape units.
The MTU9104 and MTU9105 are 9-track, 800-
bits-per-inch (bpi) units with transport speeds of 45
and 75 inches per second (ips), respectively. The
MTU9112 and MTU9113 are 7-track, dual-density,
556-/800-bpi units with transports speeds of 45 and
75 ips, respectively. The recording technique used
for all units is NRZI (Nonreturn-to-Zero-Inverted).
The magnetic tape units interface with the Level
6 Megabus by means of a Magnetic Tape Controller
(MTC9101). All input/output transfers are in Direct
Memory Access (DMA) mode, to or from main
memory via the Megabus. Tape units can be
mounted in freestanding expansion cabinets capa-
ble of housing up to two units, as shown in Figure
1-1, or mounted in the central processor cabinet.
Figure 1-1.
Level 6 System with Tape
Units
Mounted in Freestanding Cabinet
NAZI MAGNETIC TAPE CONTROLLER
(MTC9101 )
The MTC9101 provides the capability of attach-
ingmagnetic tape units as well as unit record devices
to a system with a single controller. Incorporating
sophisticated hardware and firmware, the MTC9101
microprogrammed control supports the connection
of up to four 7 -track magnetic tape units (MTU91121
9113), or up to four 9-track magnetic tape units
(MTU9104/9105), or a combination of tape units
and unit record devices (serial/line printers and card
GENERAL DESCRIPTION
1-1
Section 1
General Description
readers), with a maximum of two tape units and two
unit record devices.
Seven- and nine-track magnetic tape units can-
not be mixed on the same MTC9101; however, they
can be mixed on the same Level 6 system if a second
MTC9101 is configured. Multiple MTC9101s can
also be configured if users require extra function-
ality such as read-write simultaneity, additional
tape drives, and additional unit record devices.
Tape speeds of 45 ips and 75 ips can be mixed on the
sameMTC.
The tape units interface to the MTC9101 via a
single 9-track NRZI Magnetic Tape Device-Pac
(MTM9102) or single 7-track NRZI Magnetic Tape
Device-Pac (MTM9101). Up to four 7-/9-track tape
units are supported by either Device-Pac. An alter-
nate configuration of two 7-/9-track tape units and
two unit record devices is also permitted. The unit
record devices require their own Device-Pac.
DATA INTEGRITY AND PROTECTION
The tape units offer built-in protection against
destruction caused by an accidental write opera-
tion; before recording is permitted a write-enable
ring must be in place. All information written on
tape is immediately read and checked.
In the 7-track NRZI mode at 556 or 800 bpi,
Longitudinal Redundancy Check (LRC) characters
are generated during writing and checked during
reading to detect errors.
In the 9-track NRZI mode at 800 bpi,
Longitudinal Redundancy Check (LRC) and Cyclic
Redundancy Check (CRC) characters are generated
during writing and checked during reading to
detect errors.
Tape deskewing in the write mode is electroni-
cally adjustable. In addition, an automatic vacuum
tape cleaner reduces the incidence of data errors
caused by foreign matter on the tape.
SYSTEM AVAILABILITY
Tape unit, Device-Pac, data recovery unit, or con-
troller malfunctions are easily and quickly isolated
to their Optimum Replaceable Unit (ORU). Boards
within the central subsystem that have micropro-
gramming (firmware) like the MTC9101 have built-
in self-checking capabilities called QLTs (Quality
Logic Tests) and LEDs (Light-Emitting Diodes) for
problem indication. The QLTs are initiated in the
MTC and elsewhere in response to a Master Clear or
CFI0
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