4.3
DETAILED
FUNCTIONAL
DESCRIPTION
A
detailed
discussion
of
the
BEE
HIVE
B100
termi
nal
operation
is
contained
in
the
following
para
graphs. The Subassembly components of
the
termi
nal are functionally
interdependent,
however,
the
isolation
of
various
functions
to
the
responsible
subassembly is relatively simple. The function of
each subassembly is also described.
Schematic
diagrams are provided in Section VI of this manual.
4.3.1
Power
Supply
The
Power
Supply
provides +5, +15, +12,
and
-12
VDC voltages
to
the
circuitry from a
115
or
230
VAC
source
at
50
or
60
Hz. Figure 4-4 is a
block
diagram of
the
Power
Supply
subassembly.
The
DC regulators utilized are overcurrent
and
ther
mally
protected.
The
power
applied
to
the
Power
Supply
is
step
ped
down
in voltage.
The
transformer
output
voltages are rectified by
three
bridge circuits.
The
output
from
the
rectifiers and filters
pro
vides
power
to
the
+5, +15, +12, and -12 VDC
regulator
circuits.
4.3.2
Monitor
The
monitor
displays
data
on
the
CRT in a
pattern
determined
by
the
vertical
and
horizontal syn
chronization
signals, and
the
video
information
driving signals. A +15 VDC voltage is applied by
the Power supply to the Monitor. Appendix A
presents general and detailed data on the Moni
tor
Assembly.
a3.3
Vertical
Synchronization
Vertical synchronization is applied to the verti
cal oscillator and triggers it
at
the
vertical re
fresh rate deternmned by
the
driving logic.
The
vertical frequency is stabilized by the vertical
frequency control, which determines the point
of oscillation. The
output
pulse of the vertical
oscillator is applied to the driver amplifier
which shapes the pulse and is controlled by the
vertical linearity control. The
output
of
the
driver amplifier is applied to
the
vertical
driver by way of the height control. The verti
cal driver
output
pulse is applied to the yoke
of
the
CRT
and
causes
vertical
deflection.
The
refresh
rate
is
50
-
60
Hz.
switch
selectable.
4-6
4.3.4
Horizontal
Synchronization
The horizontal synchronization
pulses
are applied
to the horizontal amplifierwherethey are
ampli
fied and applied to the horizontal driver. The out
put of the horizontal
drive
is
applied
through
the
width coil to the yoke, where it causesthe horizon
tal deflection. The horizontal deflection signal is
also
applied
to the
flyback
transformer.
The
hori
zontaldeflection
signal
isstepped up to approxi
mately
12
KV
where
it isthen rectified, filtered
and applied to the anode cap of the CRT to pro
vide
the
high voltage required.
4.3.5
Video
Information
The
Video Information is applied
to
the
video
amp
lifierby way of the contrast control, external to
the
monitor.
The
video information signal from
the
videoamplifier isapplied to the cathode of the CRT
gun to causean On/Off condition corresponding
to light patterns of the screen. The brightness con
trol is external to the
monitor
and varies the vol
tage on the accelerating grid of the CRT.
4.3.6
Keyboard
The keyboardiscompatiblewith
ANSI
standards.
Figure3.2 defines the
ASCII
codes available.
Figure 1.2 shows the keyboard layout.
The keyboard enables the operator to manually
input information to the terminal.
When
a
key
is
depressed, the keyboard logicgenerates the corres
ponding7-bit
ASCII
code and presents the data
in
parallel
form
to the
keyboard
data
lines.
After
a short delayfor debouncing, the strobe is
driven
to
its active level and held
there
as long as
the
key
is
held
down.
For
those
keys
which
auto
repeat,
the strobe lineis
pulsed
at a 15character per
second
rate. The BREAKkey is not encoded,
but
is a func
tion
line
that
is driven low for approximately
400
milliseconds when the key is depressed.The follow
ingkeyscause
special
8-bit
(non-ASCII)
codes:
AUXSEND,
1 t ,
CLEAR/HOME,SEND,
EOS,
EOL,
and
DELETE
CHAR.
Thesecodesare
used
iplecnal
to
the
CRT
only
and
are
not
transmitted.
4.3.7
Display Organization
The main timing chain (oscillator,
dot
position
counter,
character
position
counter,
character
height counter, and character line counter)
