Timing Clock - Yamaha CS-50 Servicing Manual

[REFERENCE]
e
TIMING CLOCK
(¢,
SC, SC8)
The master clock pulse ¢ is used for synchronizing the LSI opera ton and counter, and SC8 with speed slowed down
(period extended 10 times)- which provides the interface between the digital circuit at the timing of master clock
pulse and the analog circuit.
NOTE: The SC timing pulse generated in this IC is not used for Model CS-50.
e DATA PROCESSING BASED ON Tlf/!i::-SHARING
Dividing the time base into a number of specific units (channel; in this case, one cycle of the master clock pulse, 11
ps), one data item is processed in a unit time, another data item in the next unit time, and so on. This method is
called data processing based on time-sharing. For instance, the key coder in the LSI (YM266000) processes the key
data in up to 8 channels (88ps) by time-sharing. When processing of the 8th channel is fmished, the same
processing starts again from the 1st channel. This is repeated sequentially until a new ke:r is depressed.
While the notes produced by time-sharing are shifted from one to another, in actuality,
:1'!
notes are processed
in just 88 ps and the human ear perceives them as if produced simultaneously. Thus, up to 8 note& can be produced
"at once."
¢ I
~
(j=94±5kHz)
Divided to 8
Repeat the 8 data
~D
CONTROL OF PRODUCED NOTES
Terminal
8 7
MODE, 1 0
K08 X 1
KG'7
X X
K06
X X
K05tc4
X
X
.,
K04
X X
K03
X X
K02
X X
KOl
X X
. . 0"=+8.5V
6 5 4
0 0 0
0 0 0
1 0 0
X 1 0
X X
1
X X X
X X X
X X X
X X
X
"1"=~6.5V
3
2
0
0
0
0
0
0
0 0
0
0
1 0
X
1
X X
X X
1
0
0
0
0
0
0
0
1
X
In this LSI, the number of sounds (note) to be produced simultane-
ously can be varied from 1 to 8, as desired. This manual describes
the circuit producing 4 notes used for Model CS-50. To make the
LSI produce 4 notes, set terminals MODE, K06 to K08 to +8.5V,
and K05 to 6.5V. This controls the LSI so that the new key data is
not put into the memory for the timing of channels 5 through 8,
thus limiting the key code data tv 4 notes. To set the number of
notes to another value, control th MODE and KOI to K08 termi-
nals as shown in the table at left.
NOTE: The KOl to K08 terminals designated as "0" or "1" are
used as input terminals for mode
t:•
.~~~hing
control voltage,
and those designated as "X" are 1"or output terminals for
KEY-ON signal.
e OPERATIONAL PRINCIPLE OF KEY DATA PRODUCING CIRCUIT.
The IC (YM26600) is func::tionally divided into the KEY CODER section to produce key code data representing
the depressed key and the KEY ASSIGNER section which stores the key codes for up to 4 notes in the memory
(shift registor)and outputs
tht:m
s<:queniially. The operation of the IC (YM26600) will be described below.
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