iMX8X LCDIF buffer underflow

[Kazuma_Sasaki]

Hi,

Please let me confirm some additional points for the folowing thread.

About the behavior when buffer underflow happen in LCDIF 

I understood that LCDIF will recover from the buffer underflow state by LCDIF_CTRL1n[RECOVER_ON_UNDERFLOW] setting. 

In this thread, I would like to confirm the video output from LCDIF in the buffer underflow state.

I assume that video is output to the LCD via LCDIF and video is displayed in the order shown in the figure below.

Q1. I guess that when the buffer underflow occurs, it will be displayed as following figure. Is my understanding correct?

(a) : LCDIF can not output any data during the buffer underflow state. therefore, the display become black screen.

(b) : LCDIF output remaining frame data.

(c) : LCDIF does not output any data during a blanking interval. thefefore, the display become black screen. 

Q2. Which frame is recovered from the buffer underflow state and display back to normaly? n+2 frame or n+1 frame like a following figure?

In case of n+2:

In case of n+1:

Best Regards,

Kazuma Sasaki.

[nxf63675 · Accepted solution]

Dear kazumasasaki‌,

After reviewing this with the internal team, here are the response:

For Q1, (a) is correct, LCDIF can't output data to display, DE will be invalid.

For Q2, n+1 frame will be a correct frame.The remained data for the underflow frame will not be sent to display.

Hope this help you.

Regards,

Israel H.

[Kazuma_Sasaki]

Dear Israel,

I appreciate your support.

LCDIF can not output data to display during buffer underflow state. also, the remained data too.

therefore, LCD displayed like a following figure. Is it right?

‌

(a) : LCDIF can not output any data during the buffer underflow state. the display become black screen.

(b) : LCDIF can not output remaining frame data. the display become black screen.

Best Regards,

Kazuma Sasaki.

[nxf63675]

Hi kazumasasaki‌,

We can't confirm what will happen in display side, different display can show different result when input signal is not correct.

What we can confirmed is that, after buffer underrun, the DE(data enable) signal will be invalid untill next frame.

Hope this help you,

Regards,

Israel H.

[Kazuma_Sasaki]

Dear Israel,

I appreciate your support.  I got it.

Best Regards,

Kazuma Sasaki.

[nxf63675]

Hi kazumasasaki‌,

I will review this with the internal team, as soon I get response I will get back with you.

Thanks with your patience.

Regards,

Israel H.