TS-440S
20
CIRCU IT D ESCRI PTION
2. Digital d isplay
F IP digit and segment sig n a l s a re d riven by the
6 300
but
decimal point and red character sig nals a re d riven by a tran
sistor.
8
V is used to increase the brightness of red charac
ters. The
7 800
sends display d ata serially at
1
MHz, but the
clock sig nals a re divided by two
( 500
kHz) in the
4080
and
fed into the
6 300.
Fig u re
1 6
shows how the frequency divi
sion is a ccomplished. The
7 800
sends data from its SO pin
p PD
7800G
28
46
r- -
- - - - - - - - - -
1
I
Switch un i t
I
I
+ 5 V
I
I
I
I
I
I
I
I
I
I
I
L
_ _ _ _ _ _ _ _ _ _ _,
0
85
I C 3 TC 4 0 1 3BP A/2
I I
CK
9 D
Q
13
CL PR
10
8
I C 3
SCi<
TC40 1 3 BP 8/2
4
D
26
CK
Q
2
CL PR
4
6
(pin
2 8 )
and a clock sig n a l from its SCK pin (pin
2 6 )
at ap
prox .
1
ms intervals. Afte r the
7 800
has sent
8
bits of data
five times, the
7 800
sends a negative enable pulse from port
8 5
(pin
46 ) .
When a decimal digit goes on, the
7 800
sets
port
C 4
to
L
and when a red cha racter goes on the
7 800
sets port
C3
to H .
� � = 2: ai co ,..._ l.D l() V f'l') N -
o
.D
(.> 'O
Q)
...... O'
(!) (!) Cl C> (!) (!) (!) (!) (!) (!) (!) (!) (!)
20 b i t D i s p l a y buf fer resi stor
20bit Ser i a l sh i f t resi stor
I C I
).J P D 6300C
so
Fig . 1 6 Digital circuit
3. Key scan input
The key scan input block sends key scan sig nals (negative
pulses) from its
8 2 5 5 (IC 5 3 )
port
C
in the order of
CO
to
C 7
(C 6
a n d
C 7
a re output o n ly once when the POWER switch
is turned on). When a matrix crossing point switch is on, its
Key s c a n matrix
1
2
3
corresponding bit in the
82 5 5
port A is
L
to enable the switch
to be identified . Fig u re
1 3
shows the matrix . Key scan S6
and S
7
a re provided for the extended function using diodes.
s
4
5
6
1
1
L S B
2
U S B
3
cw
4
A M
5
F M
2
6
7
8
9
0
F S K
3
V / M
M ·V
SCA N
M . I N
C L E A R
E N T
4
R IT
Z I T
T-F S E T
1 M H z
D OW N
K
5
A/B
S P R I T
A = B
2 5L
1
U . P
6
V O I C E
T . S ET O N
C L O C K 1
1 00L
3
50L
2
1 00U
8
7
T . S E T OFF
200L
4
2 5U
6
200U
9
8
T I M E R
S ET
C L O C K 2
400L
5
5 0 1
7
400U
1 0
Table
10.
Key scan matrix
