Lexicon MPX 200 Service Manual page 49

24-bit dual channel processor

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Front Panel Switches

Like the LEDs, the switches are arranged in a row-column scheme. The arrangement is in a 3x2

architecture. Whenever a button is pressed, a software scan of the SWITCH_ROW[1:0]/ bits at address

0x4C00 determines which button was pressed. The Column signals used by the LEDs are used here as

well. Each column signal is applied to a forward biased diode (D39-D41). The cathodes of these diodes

each connect to two switches. The other sides of the switches are tied in groups of three to either

SWITCH_ROW0/ or SWITCH_ROW1/.

The following table illustrates the arrangement of the switch matrix.

SWITCH_ROW0/

SWITCH_ROW1/

Resistors R28 and R29 ensure that the SWITCH_ROW[0:1]/ signals are pulled active low.

Column_2

Bypass

Store

Column_1

Edit

Compressor

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Column_0

Tap/Cancel

Load

6-13

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