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OPERATOR PANEL PUSH BUTTONS
Operator Panel Pushbuttons
Load-Rewind
Start
Rewind-Unload
Reset
2420 INTERFACE
Tape Unit Response to Pressed Pushbutton
Operative when tape unit is not in ready status. Moves tape to load point if the unit is loaded, or threads
tape to load point and loads tape into columns if the unit is unloaded.
Puts the tape unit in ready status and under computer control and turns on ready light if:
a. Reel door is closed
b. Tape is in columns
c. Tape unit is not rewinding.
Disables
all
manual controls except 'reset'.
Operative if the tape unit
is
not in ready status or rewinding and tape is in columns. Rewinds tape to load
point and unloads tape onto the file reel. Closes cartridge (if used). Opens power window at the end of an
unload operation. Opens power window if tape unit is unloaded.
Removes tape unit from ready status and computer control. Performs the following:
a. Stops tape during low-speed rewind or
b. Reduces high-speed rewind to low-speed rewind or
c. Stops tape motion during load or unload operations or
d. Turns off load check light and
e. Raises power window.
Go (TC9)
The 2420 interface consists of 24 input Signal lines, 25
output signal lines, 1 ground line, and 2 dc voltage lines.
Specifications for 2420 interface lines are given in Figure
2.
Controls tape motion; it is conditioned after the status
lines have been set to establish the operation to be
performed. The go line must be active for all operations
that move tape forward or backward, except for rewind
and rewind-unload. Tape motion is controlled internally
for these operations.
Input Signal Lines
All input lines are SLT level with a milllmum active
(down) level of +1.2 volts and a minimum inactive (up)
level of +2.5 volts.
Select (TC77,
79, 86, 88, 97, 99,
106, and 108)
Each of these eight input lines selects a particular tape
unit (0-7) from the group connected in-line to a common
control unit. An active select line gates the selected tape
unit, allowing it to receive and transmit all subsequent
signals from and to the control unit. Because the select
signal for any tape
urilt
is always taken from TC77, select
lines are rotated in each TU to TU cable. See Figure 3.
Back ward (TC
11 )
Puts the tape unit in backward status.
If
the go line is
active with 'backward status' set, tape moves backward; if
backward status is not set, tape moves forward. The tape
unit remains in backward status unless reset by 'set read
status' or 'set write status.' Since tape can only be written
forward, 'backward' sets 'read status' in the tape unit.
Set Read Status (TC25)
Sets the tape unit in read status and deconditions the
write circuits. The tape unit remains in read status until
'set write status' becomes active. 'Set read status' pre-
sumes a forward read, and, therefore, resets 'backward
status.'
3
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