Advertisement
\
\
This
produces two pulse waveforms (see Figure 4-17). The two detectors are physically positioned,
in relation to the disk segments, so that one waveform either leads or lags the other by 90 degrees.
Clockwise rotation of the tuning knob causes the output of US9 to lead that of U60 causing frequency
entered to increase. Counter-clockwise rotation causes the waveform of U60 to lead that of US9 caus-
ing frequency to decrease. The outputs of the object sensors are coupled, through resistors Rl6 and
R17, to a comparator U58A and US8B. The two inputs to this circuit are compared to a fixed dc
voltage input to the comparator from resistor combinations (R8 and RIO for U58A and R9 and R11
for U58B) which control the comparator switching point. The square wave outputs 'of the compara-
,
tor are routed to bufferU42B.
This
data buffer is enabled, from multiplexer U29, in program sequence' ,
to transfer the' encoder data tO,data lines FPO and FPl for processing as described in item 5.,
'
3. Audio and IF. Audio and IF controls and an audio phones jack are contained on the
front panel for control and monitoring of these functions. Control and audio to and from these
components are routed through the A9 circuit card from the A4 circuit card with no connection to
the in-out digital control hardware on A9. A complete description
0
f their function can be found
in Paragraph 4.3.4.
4. Liquid Crystal Displays. Two Liquid Crystal Displays (LCD) are contained on the
front panel for displaying Receiver status. Receiver frequency and BFO frequency are displayed on
LCD U3 while Receiver mode, AGC mode, tuning mode, remote/local mode, bandwidth and AF/RF
metering are displayed on LCD U4. The 8-line data bus is routed directly to ten 4-lipe LCD drivers
(UI9-U22, U36-U40 and U49) and to thirteen BCD to seven segment decoder/drivers (UIO-UI8 and
U31-U34). The ten line diivers provide decoding
aIld
drive for all annunciator· displays while the
thirteen 7-segment drivers provide decoding and drive for all numerical displays. Multivibrator U26,
timed by Rl and C8, provides a 100 Hzsignal to theDF (display frequency).inputs of the line drivers,
the BP (backplane) inputs of the 7-segment drivers and the two LCD's. :This signal is used to drive
the LCD'sdisplay..
.
. .
. . .
NOTE
LCD displays operate from low frequency square wave pulse
trains. The contrast of the display being a function of the
frequency.
Timing to the line drivers is provided by strobe signals from BCD to decimal decoder USO while the
7-segment drivers receive timing from 4-bit latch and decoder U3S. These two decoders receive their
input from binary counter US 1. The clock pulse (CP) for U51 is derived from three strobes 57, 511
and 515 combined by NOR gate U48A. Decoder U3S is controlled by inversion of strobe 57 through
U48B while USO is timed by strobe 515 through inverter US6. When a strobe signal in program time
enables a line driver or 7-segment driver, the data at its input port is latched into the driver. The
100 Hz signal on the OF or BP input of the drivers is applied to the display segments and is inverted
or not inverted through control of the data input to each driver. This in turn controls whether the
segment is turned on or off. Any segment of an LCD is turned on by a 180 degree difference of phase
between segment input and the main backplane dlive to the LCD (Figure 4-18). To turn the display
segment off the phase difference between these two signals must be zero degrees; that is, the two
signals must be in phase (see Figure 4-18).
'
5. Receiver Control Circuit Card A9, This circuitry routes data entered at the front
panel, to the microprocessor bus and routes processed data from A6A2 to various receiver functions
on A4, AS, A 7 and A8 circuit cards. This data flow in the data bus IODO through IOD7 is controlled
by read, write and address controls (lOCO through IOC7) signals from the microprocessor. All data
entered from the front panel except audio and IF functions described in item 3, is transferred to the
4-43
Advertisement
