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TS-440S
CIRCUIT DESCRIPTIO
N
2
. Digital displa
y
FIP digit and segment signals are driven by the 6300 bu
t
decimal point and red character signals are driven by a tran
-
sistor
. 8 V is used to increase the brightness of red charac
-
ters
. The 7800 sends display data serially at 1 MHz, but th
e
clock signals are divided by two (500 kHz) in the 4080 an
d
fed into the 6300
. Figure 16 shows how the frequency divi
-
sion is accomplished
. The 7800 sends data from its SO pi
n
Switch uni
t
+5v
(pin 28) and a clock signal from its SCK pin (pin 26) at ap-
prox
. 1 ms intervals
. After the 7800 has sent 8 bits of dat
a
five times, the 7800 sends a negative enable pulse from por
t
B5 (pin 46)
. When a decimal digit goes on, the 7800 set
s
port C4 to L and when a red character goes on the 780
0
sets port C3 to H
.
-------------------
-
+g
~
L
1~)
N_
O Q,
O
I()
e
M N
-
0 0 O 9 0 0 0 O U O
O
O
0
02 03 04 05 06
On 08
09 010 011 012 01
3
1
0
0
0
0 0 0 0 0 0
0 0
0
1
00
01 01 9
O
n0
1
014 01
5
o
c
20 bit Display buffer resisto
r
IC3 TC40I3BP A/2
i
f'
p P
D
7800G
46
O
28
5
C
K
D
0
CL P
R
10
8
9
13
S
I
c
LH
contro
l
circuit
20bit Serial shift resisto
r
1 1 1-
---
fl
-
>
J
IC
I
pPD6300C
s
o
s
IC
3
TC40I3BP B/
2
D
26
SCK
3
2
CL PR
Fig
. 16 Digital circui
t
3. Key scan inpu
t
The key scan input block sends key scan signals (negativ
e
pulses) from its 8255 (IC53) port C in the order of CO to C
7
(C6 and C7 are output only once when the POWER switc
h
is turned on)
. When a matrix crossing point switch is on, its
corresponding bit in the 8255 port A is L to enable the switc
h
to be identified
. Figure 13 shows the matrix
. Key scan S
6
and S7 are provided for the extended function using diodes
.
Key
scan
matrix
S
1 2
3
4
5
6
1 1
LSB
2
USB
3
CW
4
AM
5
F
M
2 6
7 8 9
0
FS
K
3
V/M
MV
SCAN
M
.IN
CLEAR
EN
T
4
RIT
ZIT
T-FSET
1MHz
DOW
N
K
5
A/B
SPRIT
A=B
25L
1
U
.
P
6
VOICE
.
T SET ON
CLOCK 1
100L
3
50L
2
100U
8
7
T
.SET OFF
200L
4
25U
6
200U
9
8
TIMER
SET
CLOCK 2
400L
5
501
7
400U
10
Table 10
. Key scan matri
x
20