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945424-9701
l'he SHIFT, CONTROL, and UPPER CASE
LOCK
keys provide the inputs
to
mode select logic,
as
shown in figure 1-20, and the REPEAT key provides its signal directly to logic on the
power/logic pwb that repeats the code from the encoder
10
times per second
as
long
as
the
REPEAT key
is
held down. The repeated code is the code for the next data key struck following
the actuation (holding down)
of
the REPEAT key.
Mode seiect iogic decodes the signais from the SHIFT, CONTROL, and UPPER CASE
LOCK
keyswitches to provide the signals labeled S 1 and
S2
in figure 1-20
to
provide the Control
an.d
Shift inputs, respectively,
to
the encoder. These inputs are used
by
the encoder
to
provide the
codes listed in table
1-5.
1.4.2
POWER/LOGIC
PWB.
Figure
1-21
is
a detailed block diagram
of
the video, audio, and
keyboard data path logic on the power/logic pwb. Figure 1-22
is
a detailed block diagram
of
the
power supply circuitry on the power/logic pwb and includes the power transformer and
capacitors mounted
off
the power/logic pwb. The following paragraphs describe the operation
of
the circuits on the power/logic pwb.
1-24
Digital
Systems
Division
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