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Last Post 02 Nov 2004 05:06 PM by
CSTN LCD Interfacing to SDK
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New Member
New Member

25 Oct 2004 02:24 PM
    I am trying to interface a 640x480 CSTN LCD to the SDK. I have read the app note discussing the signal connection and my connections agree with the app note, but I am unable to get any screen display from the DRAW-TEST command or any other LOLO commands. The backlight is illuminated and the relative timing of the signals looks OK. I am new to LCD control and I am unsure about the use of the LCDENAB signal. I am using the VIDEO-OPEN 11 16 command and then modifying several registers to accomodate the 640x480 display format. The LCDENAB signal is toggling at every horizontal line. Is this correct?
    Should the LCDENAB signal also turn on/off the LCD bias supply?
    Any insight into the purpose of the LCDENAB signal would be greatly appreciated.
    New Member
    New Member

    02 Nov 2004 05:06 PM
    This was posted under the LH7A400-10 also, here was the resposne:

    The LH7A400's LCDENAB signal (labeled LCD_MDISP on the card engine) is a AC bias signal in STN mode. In STN mode, this signal will toggle on a set number of line clocks based on the value in the ACB field of the TIMING2 LCD control register. Check out the Sharp User Guide for the description of this value and for the signal. Typically, STN displays will have a signal called 'M' which this signal should be routed to if indeed the STN spec says it is a AC bias signal. (Typically there is a diagram showing this)

    If the LCD has a 'DISP' signal, check if it is an "ON/OFF" signal or a AC bias signal. Typically it is a on/off signal. In this case, you could use the LCD_VDDEN signal, which is active high and turns on when the LCD controller comes up.

    For proper use, you'll want to make sure to design to the LCD specs' power sequencing.

    If you are struggling yet with this, I would suggest purchasing a support contract for our product service group to help with this. We have helped many customers interface to displays. Please contact the sales group if this is something you might like to do.

    Mike A.
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