IBM 727, Руководство по инструкции

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1 9 .2 .2 Hubs
Echo Bus, The write echo of the track selected by the response select switch
can be observed at this hub.
Read Bus. The output of the pre-am p selected by the response select switch can
be observed at this hub.
G o-Fb. This is the output of the go-fb trigger. This hub is used for a scope
sync when measuring start-stop time or forw ard-reverse magnet transfer time.
TU Response. Logical lines from the tape drive, as specified by the response
select switch, may be observed here.
Skew Sync. The "one" track output of the read bus is brought here for con­
venience in syncing the scope when measuring skew.
Write Pulses. Write pulses as they are sent to the tape drive are available here
when the tape drive is in " select ready and write" status, the go-backward trigger is
on, and the TI is off.
19.3 OPERATIONS
1 9.3 .1 Preparation
To operate a tape drive from the TDT, connect the signal and power cables and
turn the power on. Load the tape drive in the normal manner. Normally the tape
has a load point and end-of-tape marker, and the file-p rotect ring is not rem oved.
P ress the start button on the tape drive to put it under external control. Select the
tape drive by setting the address selector switch of both the drive and the TDT to
the same address.
Unless otherwise noted, the start-stop switch is off, the manual switch and the
TI switch are in neutral, and the go-fb switch is set to GO.
Any operations not mentioned in this section are referred to in section 19.2.
1 9.3 .2 Writing
To write, turn the read-w rite switch to WRITE, set bit switches as desired,
and push start button. If the tape indicator is not on, the tape moves forward and
all ones are written on those tracks whose bit switches are set to one. Observe
write pulses with the scope at the write pulse hub and adjust the write frequency
dial for a period of 67.2 usee between pulses. Echo pulses of the track selected by
the response select switch can be observed at the echo pulse hub. P ressing the stop
button stops the writing operation.
When the start button is depressed, a shift from the go-backward trigger flips
on the "write trigger reset single shot" sending out a 100-usec "reset write triggers"
pulse. At the same time, write pulses, already being developed as a result of the
fact that the read-w rite switch is set to WRITE, are gated out to the tape drive. Be­
cause there is no synchronization between them, it is possible that the fall of the
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