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AR# 72177

DisplayPort TX Subsystem - Why do I see a flicker when connected to a Dell U2412M

Description

When using a Dell U2412M, the screen flickers and appears black every 30 seconds to 15 minutes.

This has only been seen with designs using the 4-byte interface to the Video PHY.

Solution

The issue is due to M/Nvid values that are transferred to the monitor.

These values are slightly different than what the monitor will tolerate and it causes the screen to flicker.

This issue is fixed in Vivado 2019.1 and later versions.

To implement the fix, update register 0x94 using the driver. This is shown highlighted below.

Driver update to write register 0x94:

//xil_printf ("Dell 2412\r\n");
        //this monitor is sensitive to Mvid
        //add more accuracy to Mvid
        //Writing a value of 1 or 2 improves the accuracy
        //[3:0] - single pixel
        //[7:4] - dual pixel
        //[11:8] - quad pixel
        XDp_WriteReg(DpTxSsInst.DpPtr->Config.BaseAddr, 0x94, 0x010);

Linked Answer Records

Master Answer Records

Answer Number Answer Title Version Found Version Resolved
59384 DisplayPort TX Subsystem - Release Notes and Known Issues for Vivado 2015.4 and newer tool versions N/A N/A
AR# 72177
Date 04/25/2019
Status Active
Type General Article
IP
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