cartridge.
In
the case
of
an
index-only cartridge, the pulse train will be comprised entirely
of index pulses.
In
any event, the pulse obtained from the index notch must
be
separated
from the sector notches as appropriate. This function is performed by the time
demultiplexers
for
those situations requiring demultiplexing. The pulse obtained from the
index notch is placed onto a line separate from the other pulses.
The Lower Time Demultiplexer (zone
E16)
separates the pulse obtained from the index
notch
on
the Phase Lock Ring from the phase lock pulses. The phase lock pulses will
be
demultiplexed and output at U183, pins 10 and
13
(zone 015). The pulse obtained from
an
index notch on the Phase Lock Ring is output at U183-10 (zone 015). Only a single clock
frequency is utilized by the Lower Time Demultiplexer; this is
LC08F (zone 017) obtained
from the clock countdown in the
Start/Stop
Control Logic.
The Upper Time Demultiplexer outputs the pulse obtained from the index notch, in
index-only cartridges, at
U183,
pin 4 (zone F15). Since there are no sector notches in
index-only cartridges, there
will
be no output at U183, pin 1, for the index-only cartridge
situation. When using a multi-notch cartridge, the Upper Time Demultiplexer will output
the demultiplexed index pulse at
U183,
pin 1 (zone
E15)
and the demultiplexed sector
pulses at U183, pin
4.
The clock frequencies used with the Upper Time Demultiplexer are
determined by a jumper installed at W20,
W5,
or
W6
(zone F16). Clock LC08F, LC09F or
LC1
OF
from the clock countdown are available at W20, W5, and W6, respectively.
For both Time Demultiplexers, the specific value
of
the demultiplexing gate time is
determined by the programming array installed in
J121
(zone 0, F15). The Time
Demultiplexer functions by generating a gate
time
according
to
the value loaded into the
demultiplexer counter. The Upper Time Demultiplexer Counter (Upper Demux. Counter) is
U184
(zone
G15)
and the Lower Time Demultiplexer Counter (Lower Demux. Counter) is
U164
(zone E15). The value loaded into these demultiplexer counters is determined by the
programming array plug-in J121.
Generation
of
the demultiplexer gate is controlled by the respective Demultiplexer Control
Flip-Flop,
U203
(zone
G17)
for the Upper Time Demultiplexer and
U163
(zone
E17)
for the
Lower Time Demultiplexer. The outputs
of
U203
and
U163
are fed
to
the Upper and Lower
Time Demultiplexer Gate Flip-Flops, respectively. The actual demultiplexer gate is
obtained from the respective demultiplexer gate flip-flop. The output of the respective
demultiplexer
flip-flop
is the enabling input
to
demultiplexing gates U183-4, U183-1,
U183-10, and U183-13 (zone
0,
F15).
The time demultiplexer functions on the principle that for a pulse occurrence a gate is
generated.
If, during the
time
of
that gate, another pulse occurs, that pulse is a pulse
derived from the index notch. All other pulses are taken as being derived from other than
the index notch.
The specific demultiplexed pulses are connected
to
the Sectoring Selection Programming
array at J125 (zone
C,
0,
E,
F-14). The outputs
of
the Sectoring Selection Programming
array
are
fed
to
pulse formers and sector number counters.
The pulses obtained from the Time Demultiplexers or from the electronic sectoring
electronics are unsuitable for direct output at the
I/O
interface; therefore they must
be
formed into pulses compatible with the interface requirements. This is accomplished
by
the Pulse Formers shown in zones
G,
H5
through 9. There are four pulse formers.
One
for
the Upper
Sector Pulse, one for the Lower Sector Pulse, one
for
the Lower Index Pulse and
one for the Upper
Index Pulse.
5-38
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