Lcd Control Circuit; Memory Circuit - Sharp QA-1650 Service Manual

6.LCD CONTROL CIRCUIT
The LCD control signal is slower than the computer video signal. While the video signal is serial, the LCD
display data is given as 6-bit parallel data per R,G,and B video signal.To allow computer bit signals to be
displayed on LCD, it is necessary to store data for an entire screen in the memory and read the screen data
in accordance with the timing to drive the LCD.This is performed by controlling the FIELD MEMORY and the
LINE BUFFER with the MEMORY CONTROLLER shown as Fig.2 BLOCK DIAGRAM.
7.MEMORY CIRCUIT
7.1.Writing into FIELD MEMORY
The RGB data generated by A/D CONVERTER CIRCUIT and SIGNAL CONVERTER is written into the
FIELD MEMORY(IC3-5) by FIELD MEMORY WRITE SIGNAL and clock(FWCk), which is slightly delayed
compared to CLK. Those signals and clock are generated from MEMORY CONTROLLER.
7.2.Reading from FIELD MEMORY and Writing into and Reading from LINE BUFFER
Readout from the FIELD MEMORY is carried out using a clock (SRCK) and the control signals (prepared by.
the MEMORY CONTROLLER. Readout is asynchronous with writing.
In the normal mode data read out from the FIELD MEMORY are sent to the FIELD MEMORY/LINE BUFFER
SELECTOR and, after color correction, sent to the LCD. In the enlargement mode data read out from the
FIELD MEMORY are sent to the FIELD MEMORY/LINE BUFFER SELECTOR and at the same time to the
LINE BUFFER. When data is in the LINE BUFFER, readout from the FIELD MEMORY is stopped, and the
data is read out from the LINE BUFFER to permit enlarged display.
in the 200-line mode the display screen is designed to be automatically enlarged two times vertically.
If enlargement function is put into operation in the 200-line mode, the display screen, already set for 2-times
vertical enlargement, gives 2-times horizontal and 4-times vertical enlargement.
7.3.Displaylng menu and messages
Display data for menu and messages are stored into ROM area in IC2(M.P.U.). When such operation is
performed as pushing menu key, !C2 writes these data and address into SRAM(IC25,26) via IC1, and IC1
reads SRAM data. This data are sent to the LCD in accordance with the timing to drive the LCD.
— = > |FIELD MEMORY
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