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DS90UB954-Q1: CSI_WAIT_FS

Tomoaki Yoshida91
Genius 5255 points
Part Number: DS90UB954-Q1

Hi team,

I have questions for Reg 0x6D[7:6] CSI_WAIT_FS1 and CSI_WAIT_FS.

Questions:

When should I set this register?

How does the 954 work when this register is set?

We have an issue where the timing of the FS packet and PH do not match between the MIPI signal source imager and the MIPI receiver SoC.

I would be happy if SerDes could adjust the output timing of this FS and PH.

I would like to know if the above register settings allow such FS and PH timing adjustment.

Is it possible to adjust FS and PH timing in 954 or 953?

Best regards

  • 0
    TI__Guru** 103215 points

    Hello Tomoaki,

    By default the CSI_WAIT_FS bit will be set which means that the CSI-2 receiver will not start forwarding data in the beginning until the start of a valid frame so that you do not start forwarding out part of a partial frame when the CSI-2 output is starting up. 

    In the CSI-2 spec the Frame Start packet may also contain a 16 bit frame number count which periodically increments and resets. If this configuration is used, the serializer can be programmed to wait for the frame count of "1" before starting the forwarding using the CSI_WAIT_FS1. The usage of the frame count number is determined by the sensor configuration. 

    Best Regards,

    Casey 

  • 0 in reply to Casey McCrea
    Genius 5255 points

    Hi Casey-san,

    Thank you for your reply.

    In other words, this register cannot adjust the timing of the frame start packet and the packet header.

    Is it correct?

    Isn't it possible to adjust the time between the start of the frame and the output of the packet header in 953 or 954?

    Best regards,

    Tomoaki Yoshida

  • 0 in reply to Tomoaki Yoshida91
    TI__Guru** 103215 points

    Hello Tomoaki,

    The timing between FS and the first PH should be dictated by the CSI-2 transmitter speed. 954 has discrete CSI-2 transmitter speeds: 400Mbps, 800Mbps, 1600Mbps. It is not required per the CSI-2 standard for this timing to be specifically adjusted as it does not dictate any discrete video timing within the line time or frame time. You could try using a different CSI-2 transmitter speed and and see if it gives the desired effect but I'm not sure why you would need to adjust this time. 

    Best Regards,

    Casey