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4.2 KEY MATRIX CIRCUIT
The key matrix circuit, composed as in Fig. 4-4,
sends scan pulse to control the mode input for
decks A and B as well as program selection input.
The scan pulse decodes outputs from pins L4,75,
and 16 on the microcomputer, sending 10 m sec
pulse from pins 1 through 5 of IC 502as shown in
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Fig.4-2.
This pulse, in turn, is fed into one of the pins 17
through 22 of.IC 501 as the key matrix input cor-
responding to the key input, thus allowing the
microcomputer to send output signals matched
with key inputs to each section.
F i g . 4 - l
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Fis.4-2
Control Scan Pulse
F i 9 . 4 - 3
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