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DS90UB935-Q1: How to calculate the speed of FC？

Renf Shi
Expert 1070 points
Part Number: DS90UB935-Q1

In Non-Synchronous Clock Mode mode, why is the FPD-Link III forward channel rate 3 Gbps in the case of an external crystal oscillator of 52Mhz? Instead of 52x80 = 4.1Gbps? In addition, can a crystal oscillator greater than 38MHz be 3Gbps?

Non-Synchronous Clock Mode

I have a sensor with an output of 200M raw8, a mipi output of 438Mbps/lane, using UB90ds954 in Synchronous Clock mode, the picture is stuttering,

but switching to Non-Synchronous Clock Mode mode, using a 48Mhz crystal oscillator, only half of the image can be output, and the other half of the image is blurry

However, in Non-Synchronous Clock Mode, the image can be output normally at 54Mhz，I suspect there is something wrong with this 3Gbps setup calculation? In addition, in synchronous mode, how can the fc rate reach 3Gbps?

  • 0
    TI__Guru** 107740 points

    Hello Renf,

    Renf Shi said:
    In Non-Synchronous Clock Mode mode, why is the FPD-Link III forward channel rate 3 Gbps in the case of an external crystal oscillator of 52Mhz? Instead of 52x80 = 4.1Gbps?

    Because this device has max supported CSI throughput = 2.528Gbps which is 3Gbps of forward channel data rate.

    Renf Shi said:
    I have a sensor with an output of 200M raw8, a mipi output of 438Mbps/lane, using UB90ds954 in Synchronous Clock mode, the picture is stuttering,

    Please provide the used settings for SER and DES.

    Renf Shi said:

    but switching to Non-Synchronous Clock Mode mode, using a 48Mhz crystal oscillator, only half of the image can be output, and the other half of the image is blurry

    However, in Non-Synchronous Clock Mode, the image can be output normally at 54Mhz

    What is your CLKIN_DIV ?

    What is the REFCLK on the DES?

    Are you outputting CLKOUT from the SER to the Image sensor?

  • 0 in reply to Hamzeh Jaradat
    Expert 1070 points

    Configuration of synchronous mode

    Configuration of the Der

    0x02,0x3f, //I2c_Master_enable and output enable
0x4c,0x01, //write enable Sel: 01(port0) or 10(port1)
0x20,0x20, //disable for RX_Port1
0x1f,0x00, //CSI_TX_SPEED sel:800Mbps
0x32,0x01, //
0x33,0x43, //CSI output enable 63
0x58,0x5e, //0xbd, pass-through enable and back channel Frequency sel 5e
0x5b,0x30, //automatically load remote serializer ID
0x5c,0x30, //SER_ALIAS_ID
0x6d,0x7c, //CSI mode

    Configuration of the Ser


    0x01, 0x03, // digital reset 0/1.
0x02, 0x73, // 4-lane, Continuous Clock, gen crc, i2c 1.8v.
0x32, 0x49, // i2c pass-through, parity check.


    Non-synchronous mode

    What is your CLKIN_DIV ?

    CLKIN_DIV is the default value of 0

    What is the REFCLK on the DES?

    25Mhz

    Are you outputting CLKOUT from the SER to the Image sensor?

    no,The sensor has an independent clock

  • 0 in reply to Renf Shi
    TI__Guru 66810 points

    Hi Renf, 

    While Hamzeh is out of office, I will be helping support your request. 

    Can you provide the full script configuration? Also, to eliminate any misunderstanding, can you provide a table/summary of each result in each CLK mode & REFCLK input value along with script?

    Regards, 

    Logan