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About dropout of VSYNC and HSYNC for LCD of i.MX25

Question asked by yuuki on May 29, 2015
Latest reply on Jun 18, 2015 by igorpadykov

Dear all,

 

We connect an LCD panel to i.MX25.
(LCD:  688 x 600 / 24bpp / 44.3MHz)

 

We have the problem that a noise is over to LCD.
A white line and a black line are displayed.

 

We checked a waveform of VSYNC and HSYNC.
We found the waveform of VSYNC and HSYNC dropouted.

 

[VSYNC]   Blue: VSYNC / Aqua: DE

tek00038(VSYNC_DE).png

 

[HSYNC]  Blue: HSYNC / Aqua: OE / Red: LD

tek00036(HSYNC_OE_LD).png

 

When dropout of VSYNC and HSYNC occurred, it seems that underrun error occurs.
LISR=0x0000000B

 

Can the underrun error become the cause that dropout of VSYNC and HSYNC occurs?

If it is Yes,
May I have advice about a method avoiding Underrun error?

 

Best Regards,
Yuuki

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