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13.1.5
Key Matrix Circuit
The
key matrix
circuit reads the digit output
(pins 17 to 20) of the contorl IC (IC1) from the
Key IN terminal (pins 26 to 29) and distinguishes
different key input signals with the control IC. In
addition
to carrying out key input operations, it
PL-X420(BK)
light LEDs with output from pins 17 to 19. Fig.
13-8 shows the output waves produced by switch
matrix
input
in the following
order:
REP
SW,
Program SW 7, and EV SW.
G9)
KEY
Ge)
'N
G7}
Gs)
iéms
s4(OuT)}
Ss(PLAY) | s6(STOP)
—
ye
xe
das
@9
:
Si (REP)
S2(IN)
$3(EV)
t
fe
©
J i
L
08
9
O ,
'
=)
DIGIT
oe
| @
(7)
(ps)
ey
DS(UP)
R24
R23
R35
R26
R22
Lei)
07{D0WN)
R2)
+B2
Fig. 13-7 Key Matrix Circuit
REP
sw
ON
Control SWs all OFF
——
Naan ee
a ccaldEnE EERIE EEE
Se TEE
EEE
EeeeenteneenenOmeaInE
a
16mSEC
4mSEC
777777
}
Ic
PD2010
LEO
ON
ue
ve @
—_—__+
ae
@~
—_—
(REP.
sw
ON
J
70
SW matrix
LED matrix
[ree], [DN] veo on
ae
@~
_—_
ue @-
———_—_—__+
Fig. 13-8 Output Waveforms Produced by Key input
43
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