Interface Board Description - Micros Systems Workstation 4 LX Service Manual

WS4 Technical Overview
Optional LCD Customer Display

Interface Board Description

Figure 2-27 shows a block diagram of the LCD Customer Display interface board.
The LCD interface board is used on the Rear and Pole mount versions of the LCD
Customer Display as well as the KWS4 Operator Display.
U4, an 8-bit micro controller is the heart of this board. The device includes 64K of
on-board flash memory to store the firmware. The firmware controls all aspects of
the LCD customer display including the system board interface, graphics,
backlight, and contrast control.
The LCD Interface Board receives display data and commands through a 115K
baud serial interface. The serial interface supports in-circuit programming of the
on-board flash memory.
Microcontroller U4 establishes an 8-bit data bus, and several read/write control
signals to communicate with a pair of Epson micro controllers within the Optrex
STN LCD panel. U4 sends data and commands to the LCD micro controllers,
each of which controls a specific portion of the LCD.
To adjust contrast, U4 drives digital pot U1, providing a variable resistance to the
input of a digital to analog converter consisting of comparator U10. An on-board
DC-to-DC converter takes in +5V and converts it to -12V for the A/D circuitry.
The LCD Backlight is composed of eight White LEDs, with four on the left side
and four on the right side of the display housing. The
through Q2, drives the LEDs.
2-46
Figure 2-27: LCD Interface Board Block Diagram
PWML
Workstation 4 and 4 LX Field Service Guide
output of U4,