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AM5728: DPI manual I/O timings

Thomas Yang55737
Expert 5176 points
Part Number: AM5728

Hi  Expert

Q1

In AM5728 datasheet DPI video output session, there are 4 kinds of timing, (table 7-15~ table 7-18)

Table7-15: tc(clk) Cycle time, output pixel clock vouti_clk  min is 11.76

All of table 7-16~18, tc(clk) min is 6.6,  how to decide choose which one(16 or 17 or 18) if external connected LVDS adaptor requires min of tc(clk) is 6.6

Table 7-15. DPI Video Output i (i = 1..3) Default Switching Characteristics

Table 7-16. DPI Video Output i (i = 1..3) Alternate Switching Characteristics

Table 7-17. DPI Video Output i (i = 1..3) MANUAL3 Switching Characteristics

Table 7-18. DPI Video Output i (i = 1..3) MANUAL4 Switching Characteristics

Q2

What is  A_delay and G_delay exactly mean?

Refer to AM5728 TRM, I know how to set CFG register value according to A_delay and G_delay value, but I don't know what A_delay and Q_delay meaning themselves?

Thanks

  • 0
    TI__Guru**** 393215 points
    Hi,

    See section 18.4.6.1.6 in the AM572x TRM Rev. I.
  • 0 in reply to Biser Gatchev-XID
    TI__Expert 5176 points
    Hi Biser
    I read this session before and know how to calculate the register value based on A-Delay and G-Delay, but my question is what is A-delay and G- delay meaning? How to influence the timing after we set these two value?
    Also Q1 still needs to be answered, thanks!
  • 0 in reply to Thomas Yang55737
    TI__Guru**** 161600 points

    Hi,

    but my question is what is A-delay and G- delay meaning? How to influence the timing after we set these two value?

    @a_delay: Agnostic Delay (in ps)

    @g_delay: Gnostic Delay (in ps)

    You can see the definition of most of the parameters in iodelay driver: drivers/pinctl/ti/pinctrl-ti-iodealy.c, as this is not specified in the documentation.

    How to influence the timing after we set these two value?

    These values are written in CFG_x_IN, CFG_x_OUT & CFG_x_OEN registers (for reference see dra74x-mmc-iodelay.dtsi). They are used to ensure that the corresponding interface IO timings are met.  The values are written to the BINARY_DELAY bit field and Indicate the number of coarse (9:5) and fine (4:0) delay elements to be used on the delay line connected to this pad.

    Also Q1 still needs to be answered, thanks!

    Following the description in the TRM: Section 18.4.6.1.4 IOSETs through Section 18.4.6.1.8 IO Delay Recalibration, you can see which IO Delay modes are supported by the VOUT interface, that you use:

     The modes requiring Virtual IO Timing Modes are described in Virtual Functions Mapping tables within the “Timing Requirements and Switching Characteristics” section of the Data Manual.

     The modes requiring Manual IO Timing Modes are described in Manual Functions Mapping tables within the “Timing Requirements and Switching Characteristics” section of the Data Manual.

    If you read carefully section 7.7 Display Subsystem – Video Output Ports of the device Data Manual, you will see that the VOUT supports only MANUAL timings mode. Given your statement: "external connected LVDS adaptor requires min of tc(clk) is 6.6", you will need to use the Alternate Switching Characteristics -> those are the VOUT1_MANUAL1, VOUT2_IOSET1_MANUAL1, VOUT2_IOSET2_MANUAL1, or VOUT3_MANUAL1 (SEE Table 7-2. Modes Summary from the Data Manual).

    Best Regards,

    Yordan

  • 0 in reply to Yordan Kovachev
    TI__Expert 5176 points

    Hi  Yordan,

    Thanks! From below info, Alternate switching/Manual3/Manual4, all of these 3 modes support Min of Tc(clk) = 6.06ms, so I am consufsed about why user need to choose Alternate switching(Manual1) mode, not Manual3/4 mode. I checked DS and TRM again, but still didn't find the guide. Maybe I missed something in my understand, could you help on this question?

    From datasheet, DPI Vout supported mode:

  • 0 in reply to Thomas Yang55737
    TI__Guru**** 161600 points
    The cycle time is the same, but all other timings are different.
    You can see, for example, in Manual Mode3 the maximum delay time for DPI1 is 5.56ns and for DPI2 and DPI3 the maximum delay time is 5.91. In Manual Mode4 the maximum delay time for DPI1, DPI2 and DPI3 is 6.61.

    Similarly in Manual mode3 the minimum delay time is 2.85ns for DPI1 and 2.78ns for DPI2 and DPI3, while in Manual Mode4 the delay time is 3.55ns. And, when using Alternate Switching characteristics the timings are different.
    You need to choose, depending on the timing requirements in your application.

    Best Regards,
    Yordan