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3.
Write Data
4.
Side Select
The Read Data composite signal
is
sent to the user system via the
interface.
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Figure 1-3
FM Recording Magnetization Profiles
1.16.6.1
Data Recording
The write electronics consist of a Write Current Source, a Write Waveform Generator, an Erase Current Source,
the Trim Erase Control Logic, and the Head Select Logic (see Figure 1-2).
The read/write winding on the magnetic head is center-tapped. During a write operation, current from the Write
Current Source flows in alternate halves of the winding, under control of the Write Waveform Generator.
The conditions required for recording, i.e., unit ready, must be established by the user system, as follows:
1.
Drive speed stabilization occurs 250 msec after the drive motor
is
started.
2.
Subsequent to any step operation, the positioner must be allowed to settle. This requires
20 msec after the last step pulse is initiated,
i.e.,
5 msec for the step motion and 15 msec
for settling.
3.
The foregoing operations can be overlapped,
if
required.
Figure 1-4 illustrates the timing diagram for a write operation
.
At t
=
0, when the unit is ready, the Write Enable in-
terface line goes true. This enables the Write Current Source.
The Trim Erase control goes true 390 msec after the Write Enable
interface
line since
the trim
erase gaps are be-
hind the read/write gap. It should be
noted
that this value is optimized between the requirements at Track 00 and
at Track 39, so that the effect of the
trim
erase gaps on previous
information is
minimized
.
Figure 1-4 shows the
information
on the Write Data interface line and the output of the Write Waveform Genera-
tor, which toggles on the leading edge of every Write Data pulse.
Note that a minimum of 4 usec and a maximum of 8 usec between Write Enable going true and the first Write Data
pulse is only required if faithful
reproduction
of the first Write Data Transition
is
significant.
At the end of recording, at least one additional pulse on the Write Data
line
must be inserted after the last signifi-
cant Write Data pulse to avoid excessive peak shift effects.
1-9
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