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3-6
Theory of Operation
The following operations are performed when writing data. These operations may be over-
lapped if required.
Figure 3-5 shows the rei event timing diagram for a write operation. At T
=
0 when the unit is
ready, the write enable line goes low. This enables the write current source and bias circuit-
ry.
Since the trim erase gaps are behind the read/write gap, the TRIM ERASE control goes true
390 f.1sec. after the WRITE ENABLE interface line.
It
should be noted that this value is
optimized between the requirements at Track 0 and Track 34 so that the effect of the trim
erase gaps on previous information is minimized.
Figure 3-5 shows the information on the WRITE DATA interface line, and the output of the
Write Waveform Generator which toggles on the leading edge of every WRITE DATA pulse.
At the end of recording, at least one additional pulse on the WRITE DATA line must be
inserted after the last significant WRITE DATA pulse to avoid excessive peak shift effects.
The TRIM ERASE signal must remain true for 800 f.1sec. after the termination of WRITE
ENABLE to ensure that all recorded data are trim erased. This value is again optimized
between the requirements at Tracks 0 and 34.
The duration of a write operation is from the true-going edge of WRITE ENABLE to the
false-going edge of TRIM ERASE. This is indicated by the internal WRITE BUSY waveform
shown.
WRITE ENABLE
NOTE1
NOTE2
I
I
I
I
~~
~--+----+----+----1~-+----+----+-.
.
I
800
I
TRIM ERASE
- t - - - - + - -
~
--I
I
fJ.
SECS
r-
INTERNAL
WRITE BUSY
~--+-~-~--+---+--~I-~'~
f - - - - t - - - - + - - - - i - - - - 1 t - - - - - - i - -
--+---.....,ll--~\ ~
NWR ITEDAT A
- t - - - - - - - l i
r---r
WRITE
WAVEFORM
- t - - -.........
GENERATOR
WRITE CURRENT
NOTES:
1.
1
~
a
=
250 Milliseconds after drive motor
2.
Unsynchronized
starts or 20 milliseconds after last step
pulse, (whichever
IS
the latest time)
3.
8.5 ma peak to peak
4.
4
fJ.
seconds minimun. 8
fJ.
seconds maximum
Figure 3-5:
Write Timing Diagram
I
I
I
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