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e. Serial Data Circuit (SO, SI and DATA)
Centering PD40508, the three microcomputers communi-
cate with each other using a data line or bus. PD4050B peri-
odically gives PD4022B
or PD4046B
a command,
and
PD4022B
or PD4046B
responds
it. The command
and
response are transmitted in the form of 8-bit serial data. The
data bus also allows the 80-bit serial display data to pass.
The waveforms of the signals on the bus (or at the SI termi-
nal of each computer)
observed
on an oscilloscope
are
shown in the circuit diagram. Still waveforms are unavaila-
ble because they always vary quickly. Three examples of the
waveforms have been illustrated in the circuit diagram. The
data communication among the computers can be deemed
to be normal as long as a waveform similar to the example
can be observed at SI and DATA terminals because the form
on the oscilloscope screen flows and never stays still.
The transistors connected to each output terminal (SO) of
the computers work as invertering buffers. There will be no
problem with the input and output connected to the same
- :
line because a command has a code which fits a particular
computer, and each computer accepts only the input sig-
nal which has a code fit to it.
f. SCK
This terminal puts in or out synchronizing clock signals for
controlling serial data transmission. When talking, the com-
puter is in the output mode and, when listening, in the in-
put mode and
it accepts
SCK signal from
the talking
computer. At this time, talker's SCK data appear on the bus
in series. The waveform of the signal on the SCK terminal
observed on the oscilloscope is as shown in the circuit dia-
gram. The still form of this wave is also unavailable with an
ordinary oscilloscope.
g. CS
PD4050B does not put out a command with the code ex-
plained above for DISPLAY but puts out a CS signal -(L pulse)
from #48 synchronizing with its 80-bit serial DISPLAY data.
PD7005
accepts
the
DISPLAY
data
coming
from
PD4050B
#15 (SO) only when C$ is L (OV), then decodes
and displays them. It is also impossible to observe the still
waveform of these data on the oscilloscope.
ICI
PD4022B
IC7
H:1uS/div
5
V:1V/div
H:2mS/div
V:1V/div
c2
PD4050B
Ici
PD7005A
H:1yuS/div
:
50
$23 : CLEAR(CANCEL)
V:1V/div
ACC ON : H(5V)
:
vOD
VDD
R129
5V
<2
R122
Ri2t
C23
1D
R5I
iS
R61
Q33
Q34
Q20
D3!
R123
<\ 0.8V
[ove |
DIS
A
OH
bc
ma
ey,
C25 [C26
Rt24
T
T
R60
Y)
Fig. 24 Basic circuit for operating the system
18
PD4046B ©
D8
Lene RET
tet
RS
O Back—up +B
a o e epee
With tuner(F X-T8) connected.
H:1uS/div
H:0.2S/div
V:1V/div
H:2uS/div
V:1V/div
193
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