Sony ICF-6800W - Page 19

Segment Decoder
The purpose of the segment decoder is to change
the output signals of the decimal counter to the
signals that illuminate the corresponding segment
(a—g) of the LED. i
The segment decoder operates as shwon below.
When the figure “‘2’’ is displayed, for example, the
signals shown in Fig.38 are sent as the output signals
from the segment decoder.
FIGURE “2”
COUNT SEGMENT
SIGNALS SIGNALS
0 a I
b am
c 0 f
— Qed
\ 7 | f pe
t 0 —
0 g | qd
SEGMENT
DECODER
DISPLAY COUNT SIGNAL SEGMENT SIGNALS
a bc de fg
0 0000 tk Fo ch Pf i 0
1 0001 0 1 1 0 0 0 0
2 0010 Mle “Orde cle Oe oc
3 0011 Ay: lw <beela MOY 200 ol
4 0100 0 1 1 0 0 21 21
5 0101 1 0 1 212 0 1 21
6 0110 1 0 1 #212 #721 ~=21~21
7 0111 1 1 1 0 0 1 =0
8 1000 deo ads Die oe Ie 2
9 1001 1 1 21 #2 =0 1 21
Fig. 38
Segment Driver
This amplifies signals generated by the segment
decoder to the level which required to operate the
LED segments.
Digit Decoder
This generates signals for the multiplexer and
the digit driver simultaneously.
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| ICF-6800W
Digit Driver
As previously mentioned in the explanation
of the multiplexer, this IC provides the ““Dynamic
Drive” for the LED display. This illuminates the
Ist to the 5th digits in order. Q62—Q66 control
the on-off operations of each digit’s LED. The on-off
signals are sent to Q62—Q66 by the digit driver.
Fig. 39 shows an example of the timing of
the outputs for displaying 1, 2, 3, 4 or 5. These
waveforms are shown in ideal form. Actual wave-
forms are much distorted. The outputs are put
out when both the digit and segment outputs are
in high level.
Zero Suppress
Zero suppress is the circuit which disables
display of zeroes preceeding the significant figure,
as shown below.
example: 00 100 kHz
These O figures are not displayed.
IF Selector
Since the frequency of the VCO1 is 29.055MHz,
the counter would indicate 29.055 MHz if counted
as it is, even if one wishes to display 10 MHz when
receiving SW.
In order to get a display of 10MHz, 1) MHz
must first be subracted from the VCO1 frequency.
The I-F selector performs this subtraction. The
counter has a display of five digits. If O000(is set
to be displayed when 19055 is applied, 00001 kHz
is displayed when 19.056 MHz is measured.
In order to get this performance, a signal from
which 19056 is subtracted should be applied when
resetting the decimal counter for the next couni,
These figures are calculated as follows.
100000 — 19055 = 80945
6 units
The figure 80945 should be set in the cunter
before counting a given frequency.
When 19055 is counted, the display «f the
counters becomes 0, since 19055 + 80945 = 1010 00.
1 in the sixth digit is not displayed, sinc: only
5 figures are displayed.
The IF selector selects the figures to setin the
counter before counting. The following ig.ures
are set by the IF selector in this system.
FM 89200
MW 99545
SW 80945 (WIDE, NARROW)
80943 (USB)
80947 (LSB)