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THS8200 VGA Settings

Ryan Pak
Prodigy 10 points
Other Parts Discussed in Thread: THS8200

Hello,

 

I am trying to set up the THS8200 to output a 640x480 VGA signal.  The THS8200 is working along with an LCD Controller in the NXP LPC2478 ARM7 Processor.  The LCD controller outputs 24 bit RGB signals along with H-sync and V-sync data and a clock of 24MHz.  Everything looks right on the digital side of the circuit as far as we can tell.  Right now, it seems there is a synching problem.  For example, when I try to display a single vertical line, the line is repeated about 10 times and slopes diagonally from top right to bottom left. Currently, the registers we have set are:

Sub-address; value
0x03; 0xC1
0x19; 0x03
0x1C; 0x70
0x34; 0x03
0x35; 0x20
0x36; 0x00
0x37; 0x01
0x38; 0x87
0x39; 0x22
0x3A; 0x0D
0x3B; 0x0D
0x3C; 0x80
0x4A; 0x8C
0x4B; 0x44
0x4C; 0x00
0x4D; 0x00
0x4E; 0x00
0x4F; 0xC0
0x70; 0x60
0x71; 0x00
0x72; 0x01
0x73; 0x03
0x74; 0x00
0x75; 0x01
0x76; 0x00
0x77; 0x07
0x78; 0xFF
0x79; 0x00
0x7A; 0x00
0x7B; 0x00
0x7C; 0x00
0x82; 0x43

If anyone has any advice to help resolve this problem.  Please let us know.

Thank you.

 

  • 0
    TI__Genius 16810 points

    Ryan,

    Your settings are indentical to those we have used with the exception of REG36h.  If the FID input pin is pulled or driven low for progressive discrete sync formats, use REG36h=80h when FID polarity is set to low polarity in REG 82h.

    This may not be your problem, however.  For VGA60Hz, Pix clock=25.175Mhz, total line/frame = 525, and total pixels/line=800.  The output line rate and frame rate will be incorrect if the THS8200 inputs do not match this standard timing.