Register Summary - Lexicon 960L Service Manual

960L Multi-Channel Digital Effects System Service Manual
LCD Backlight (sheet 7)
The backlight built into the color LCD module is based on a Cold Cathode Fluorescent Lamp (CCFL), which
requires high-voltage ac to operate. This voltage is generated by the inverter module mounted in the LCD
display housing. The inverter is rated to produce an output of 900VACrms from for an input voltage of 5 to
12 VDC. Regulator U4 (LM2941) supplies this input voltage and protects the inverter by going into
regulation if the input is too high due to misconnection. U4 is a low-dropout type and normally delivers
nearly full voltage to the inverter, with only around 1/2 volt across the regulator itself.
On/off and brightness of the LCD backlight is determined by the control characteristics of the inverter
module, from control lines connected along with the dc power via J2. Logic level LCD_VBR from the cpu
switches transistor Q2 to set brightness control voltage VBR/ for two brightness levels, from 0Vdc (bright) to
1.6Vdc (dim). Logic level LCD_VRMT/ drives transistor Q1 to switch the on/off control VRMT between +5V
(backlight on) and ground (backlight off).
Main 5V (sheet 9)
The main +5V logic supply is derived from +12V by switching regulator U40 (LM2676). The switching pulse
waveform at pin 1 (SW) of U40 is filtered by L1 and C15 to produce +5Vdc, which is the average value of
the pin-1 voltage. The positive excursion of the switching pulse is produced by the series switch within U40,
which connects pin 1 (SW) to pin 2 (VIN), which is the main +12V heavily-decoupled by FB5 and associated
capacitors. When the switch is off, the negative excursion of the switching pulse drops to a fraction of a volt
below 0, determined by the forward voltage of catch diode D25. The switching frequency remains constant,
at around 260 kHz. The regulator senses the filtered 5V fed back into pin 6 (FB) and varies the switching
duty cycle to maintain regulation. The switching regulator efficiently converts the relatively high-voltage low-
current 10-to-12V input into the low-voltage high-current 5V output. At lower input voltages, the regulator
draws more current to provide the constant power consumed by the 5V output load.
3.3V and 2V (sheet 9)
The 3.3V logic supply is derived from the 5V by a fixed-voltage, linear regulator, U3 (LM3940). The 2V logic
supply is derived from the 5V by adjustable linear regulator U7 (LM317), set to 2V by R34/R35.

Register Summary

The following is a full map of the physical address space (all addresses in hex):
Address
0000 0000 – 0001 FFFF
0800 0000 – 087F FFFF
1000 0000 – 1000 001C
1000 0100
1000 0102
1000 0104
1000 0200
1000 0300 – 1000 030E
1000 0310
1000 0312
1000 0314
1000 0316
1000 0400
1000 0402
1000 0404
1000 0500 – 1000 05008
1000 0600
1000 0700
7-50
Symbol Name
Boot flash
Program flash (alternate)
MTRWFn Motor waveform register
MTRENA Motor enable register
MTRDIR Motor direction register
MTSHR Motor Shift Rate
ADCMD A/D command register
SLDPOSn Fader n position register
JOYSTKX Joystick X-axis register
JOYSTKY Joystick Y-axis register
P12VSEN Plus 12 volt sense register
TAPDR Tap data register
METER0 Meter bridge register0
METER1 Reserved for Meter bridge register1
KEYLED Keypad LED Register
KEYDAT Keypad data registers
TCHDAT Touch data register
PS/2DDAT PS/2 Data Register