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Set Write Status (TC13)
This input line puts the tape unit in write status and
conditions tape unit write circuits. The tape unit remains
in write status until 'set read status' or 'backward'
becomes active. 'Set write status' also resets 'backward
status.'
Note: Because write checking is accomplished by reading,
read circuits are conditioned during both read and write
operations.
Write Bus (TC1,
3,
q,
17, 19,21,31,33,
and 35)
These nine input signal lines (0-7 and P) gate data from
the tape control directly to the write head drivers. Data
sent by the tape control determines time and duration of
write head flux reversals.
Rewind (TC39)
This input line causes the tape unit to perform a rewind
operation (tape is rewound to the load point). Rewind is
at high speed if there is more than approximately 60 feet
of tape on the take-up reel; otherwise, it is a low speed
rewind.
Rewind-Unload (TC41)
Like rewind, this input line causes tape to rewind to load
point. In addition, tape unloads, and the power window
opens, preparatory to changing reels.
Metering Out (TC23)
This input line is active when the system's conditions are
met for running usage meters and the control unit is not
off-line. The tape unit meter stops only if the metering-
out line becomes inactive, if the tape unit is unloaded and
not rewinding, or if the tape unit is at load point.
Metering out is terminated in each individual tape unit.
Output Signal Lines
All output lines are SLT level with a minimum active
(down) level of +0.3 volt and a minimum inactive (up)
level of +2.5 volts.
Models
1, 2, 3
(TC180,
182,
and 184)
These output lines identify the tape unit model and
indicate the tape unit is selected and ready. All three lines
(1, 2, and 3) active at the same time identify a model 7
tape unit.
Select and at Load Point (TC198)
Indicates the tape on the selected tape unit is pOSitioned
at load point. This line
is
reset if the tape is unloaded and
not rewinding or if tape is moved forward.
6
Select and Not File-Protected (TC192)
Indicates that a selected and ready tape unit can perform
a write operation because it is not file-protected. A tape
unit is file-protected (writing or erasing of tape is
prevented) when the file reel does not contain a write-
enable ring.
Select and TI Off (TC196)
Active when the tape indicator of the selected tape unit is
off; this indicates the selected tape unit has not reached
the useful end of tape. TI is set by sensing the light-
to-dark transition at the end of the EOT marker during a
forward operation; it is reset by sensing the light-to-dark
transition of the opposite end of the same marker during
a backward operation.
Select and Read Status (TC162)
This output line indicates read status when active, and
write status when inactive; it is effective only while model
1, 2, and 3 lines are active.
Not Ready (TC142,
144, 156, 158, 172, 174, 186,
and
188)
This output line indicates the addressed tape unit (0-7) is
connected but not ready. A tape unit is not ready if it is
unloaded, in reset status, or performing a rewind opera-
tion.
In a tape unit configuration that utilizes a 2816
Switching Unit, the active state of 'not ready' may also
indicate the tape unit is switched; that is, the tape unit is
operating with another control unit. Because a selected
tape unit sends its own 'not ready' signal out on TC142,
not ready lines are rotated in
TV
to
TV
cables. so the
tape unit next to the control unit has the 'not ready (n)'
line at the proper TC pin. See Figure 4.
On a rewind-unload command, the tape unit drops the
model lines (TCI80, 182, and 184) before activating the
not ready line.
Read Bus (TC82,
84, 93, 95,
102, 104,
113, 115,
and 122)
These nine output lines (0-7 and P) carry the data read
from tape to the tape control for a read operation and
for checking a write operation.
Backward Status (TC164)
This output line is active when the tape unit is in
backward status. Conditioning the go line causes back-
ward motion of tape-for example, in backspacing.
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