Lcd Interface; Backlight Interface - Micros Systems Workstation 4 LX Service Manual

WS4 LX Technical Overview
TFT LCD and Backlight Interface
LCD Interface (REF: ABRD86 - Sheets 5 and 27)
LX800 Pixel Data outputs DRGB[23:2] are fed to U26, a SN75LVDS84A FlatLink
Transmitter. This device contains three seven-bit parallel-load serial-out shift registers
coupled to four low voltage differential signaling (LVDS) line drivers. The primary
function is to convert the 21-bits of Low Voltage TTL level pixel and clock data from
the LX800 TFT Controller into three data streams and a single clock stream. The
output of U26 drives system board connector J3.
The primary reasons for converting the TTL/CMOS level video signals to the LVDS
format are reduced noise and cable pin count. The LVDS compatible signals are
converted to TTL/CMOS voltage levels within the LCD Panel.
LCD Panel power sequencing is provided by the
LX800 TFT controller. This signal drives a switch consisting of Q9 and Q8.
VDDEN_VIPSYNC
become stable the processor is executing instructions.

Backlight Interface

The backlight enable signal,
enable signal is ANDed with
backlight inverter mounted to the LCD panel.
fan controller in Super I/O U36.
The WS4 LX API manages the backlights through the LX800 TFT controller. It
contains a set of fixed PWM values for the BRIGHT, NORMAL and DIM brightness
settings and defines a range of values for each setting. Each time the API starts, it
loads a file called DOC\HWInfo\ddi_gx_sharp.inf. This file contains modified
brightness and range settings that override those in the API. For example, the
ddi_gx_sharp.inf file was recently modified to handle the change-over from the Sharp
LG41 to the Sharp LG61 LCD.
4-14
does not go active until all system voltages and busses have
DISPEN originates in the LX800 TFT controller. This
at U23 to produce
SIO_PWM
Workstation 4 and 4 LX Field Service Guide
output of the
VDDEN_VIPSYNC
which drives the
PWMBL
originates from an unused
SIO_PWM
TM