REWIND. —The rewind operation consists of
reverse tape movement at 200 ips. Tape movement is
slowed to 120 ips when less than 100 feet of tape (low
tape) remains on the take-up reel. Tape movement is
stopped upon detection of BOT marker.
MTU Offline Operations
You can operate the MTU offline using the
maintenance panel. The maintenance panel
pushbuttons can be used to generate all operational
commands and the indicators monitor the results of
these operations. In addition, some MTUs contain an
internal microprogrammed controller (MPC) read-only
memory (ROM). MTUs with an MPC ROM can be
programmed by the manufacturer to perform internal
diagnostic programs, offline operations, such as tape to
printer, tape to card punch, and card reader to tape.
MTU Functional Description
A typical MTU is divided into the following
functional areas as shown in figure 9-16:
Control unit (CU)
System control panel
Maintenance panel
Magnetic tape transports (MTT) 1 through 4
CONTROL UNIT. —The control unit contains the
logic required to control the various functions of the
magnetic tape unit and to perform the tasks required by
the external computer(s). At the heart of the control unit
is the MPC. The MPC acts as a data switch and
controller for all data transfers and other operations
within the tape unit. The MPC is a microcomputer with
arithmetic and control capabilities.
Figure 9-16.—An MTU functional block diagram.
9-13
