DOUBLE FREQUENCY
WRITE
DATA
WRITE DRIVER
OUTPUT
WRITE CURRENT
(CURRENT LOOP)
DISK
FLUX
PATTERN
HEAD READ SIGNAL
DIFFERENTIATED
READ SIGNAL
RAW
DATA
READ PULSE
OUTPUT
C
C 0 c
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I
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c a c
c
I I I I I I I I
I I I I I I I I
~
I I I I I I I I
I I I I I I I I
6 I
~.c:r:>..
I A I /
I
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1-
~
I
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I
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I I I I I I I I
I I I I I I I I
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I I I I I I I I
I
I I I I I I I
I I I I I I I I
C - CLOCK TRAIllSITION
1 -
DATA
"ONE"
PRESENT
a
-DATA
"ZERO"
PRESENT
Figure
4-3.
Double Frequency Recording Flux and Pulse Relationship
4.6 REAOIWRITE ELECTRONICS
The
Read/Write electronics are contained
on
a single PCBA. Figure 4-4* is a functional
block diagram
of
the 03000 Read/Write system and should
be
referred to for the following
discussion.
4.6.1
HEAD SELECT
Head
selection in the 03000 is accomplished by signals from the using system via the
Platter Select
(IPXSR) and Head Select (IHSXR)
I/O
interface lines. The signals
on
these
lines are required to select one
of
four read/write heads. Table
3-1
shows the head select
decoding used in the
03000 Disk Drive.
4.6.2
WRITE ELECTRONICS
Information
to
be
recorded is supplied to the disk drive via the Write Data Signal (IWDSR)
1/
0 interface line.
The
writing process is under complete control
of
the logic functions
and
control circuitry (Paragraph 4.7). Verification
of
system readiness, a software function, is
required prior to initiation
of
a write operation.
The
conditions that must
be
satisfied
before a write operation
can
be performed are:
(1)
The unit must
be
in the Ready condition and Selected. This implies that only one
head
is selected.
(2)
The heads must
be
positioned over a legal track address.
(3)
The
WRITE
PROTECT
switch for the disk selected is switched to the OFF position
and
the Power Clear signal is at a high level.
*Foldout drawing,
see
end
of
this section.
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