Lexicon MPX 200 Service Manual page 48

MPX 200 Service Manual
LED_ROW18/ 2
LED_ROW19/ 3
LED_ROW20/ 4
U2 data bits FRNT_D[7:5] are active high and they activate the three columns; the columns are connected
to the LED anodes, so the column signals are by necessity active high. As can be surmised, a write must
be done to this address whenever the software tries to turn on any LEDs at all. The data that is latched into
this register for these data bits are inverted by three of the gates inside U1. The resultant inverted bits are
then used to activate three transistors (Q1-Q3) that provide enough current to light the LEDs in each
column. Since these transistors are PNP types, a second inversion takes place. It could be thought of as
writing a logic 1 to any of these three bits and they are current boosted to drive the LED anodes. These bits
are continuously written by software in a cyclical fashion; no more than one of these bits is active at any
given time.
The next table illustrates the column arrangement as it pertains to these three data bits.
Address: 0x4C04
Write Only
Active Row Bit 5 (Column 0)
LED_ROW0/ D23 (Dual Stereo)
LED_ROW1/ D32 (Threshold:EDIT)
LED_ROW2/ D25 (Mono Split)
LED_ROW3/ D26 (Dual Mono)
LED_ROW4/ D15 (Plate)
LED_ROW5/ D12 (Chamber)
LED_ROW6/ D29 (EQ)
LED_ROW7/ D35 (Load Button LED)
LED_ROW8/ D11
LED_ROW9/ D20 (Ambience)
LED_ROW10/ D38 (Store Button LED)
LED_ROW11/ D14 (Echo/Delay)
LED_ROW12/ D2 (L_MID)
LED_ROW13/ D4 (R_CLIP)
LED_ROW14/ DISP3 (Segment F)
LED_ROW15/ DISP3 (Segment G)
LED_ROW16/ DISP3 (Segment E)
LED_ROW17/ DISP3 (Segment D)
LED_ROW18/ DISP3 (Segment C)
LED_ROW19/ DISP3 (Segment B)
LED_ROW20/ DISP3 (Segment A)
De-coupling capacitors are distributed evenly throughout the front panel PCB and provide power supply de-
coupling for the 5V digital line.
Sheets 2 and 3
These sheets show the non-button related LEDs. The previous section illustrates the row-column
arrangement of these LEDs. No further discussion on this page is necessary.
Sheet 4
This sheet shows the arrangement of the Front Panel buttons and their respective LEDs. The LEDs have
been covered in previous sections, and no further discussion will take place here.
6-12
DISP3 (Segment C)
DISP3 (Segment B)
DISP3 (Segment A)
Data Bus Bits (FRNT_D[7:5])
Bit 6 (Column 1)
D21 (Chorus)
D24 (Cascade)
D33 (Attack)
D17 (Flange)
D27 (Mix)
DISP2 (Segment A)
D5 (R_MID)
DISP2 (Segment F)
DISP2 (Segment G)
DISP2 (Segment E)
DISP2 (Segment D)
DISP2 (Segment C)
DISP2 (Segment B)
DISP2 (Decimal Pt)
D7 (Threshold: Compressor)
D18 (Rotary/Tremolo)
D1 (L_Clip)
D36 (Edit Button LED)
D8 (-3dB)
D6 (R_Signal)
D43 (Tap/Cancel Button
D8 (-3dB)
D6 (R_Signal)
D43 (Tap/Cancel Button
DISP1 (Segment F)
DISP1 (Segment G)
DISP1 (Segment E)
DISP1 (Segment D)
DISP1 (Segment C)
DISP1 (Segment B)
DISP1 (Segment A)
D28 (Adjust)
D19 (Hall)
D30 (Lvl/Bal)
D13 (Gate)
D22 (Pitch/Detune)
DISP1 (Decimal Pt.)
D16 (Room)
D31 (Ratio)
D34 (Release)
D37 (Compressor Button
D3 (L_Signal)
D42 (Bypass Button LED)
D9 (-10dB)
D10 (-20dB)
D42 (Bypass Button LED)
D9 (-10dB)
D10 (-20dB)
Bit 7 (Column 2)