• State
  • Locked Locked
  • Replies 4 replies
  • Subscribers 34 subscribers
  • Views 94 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LMH1219: Regarding data when the LMH1219 LOCK_N pin is High

user272328
Prodigy 180 points

Part Number: LMH1219
Other Parts Discussed in Thread: LMH1218,

I am implementing a 3G video loopback setup (using an Altera sample design) with the LMH1219, LMH1218, and an Altera FPGA.
I have confirmed that the input video is correctly output in the "SDI input -> LMH1219 -> FPGA -> LMH1218 -> SDI output" configuration.
However, when using an optical SFP module for the input, no video is output.
Upon investigation, I found that while the LOCK_N signal goes Low for the SDI input, it remains High for the SFP input.
When LOCK_N is High, is the data output from the LMH1219 in a valid state?
Also, could this be the reason why the loopback is not functioning?

 

  • 0
    TI__Mastermind 38295 points

    Hello,

    When LOCK_N is high, the reclocker has not locked onto the receive datastream. This signal should pull low once the LMH1219 is locked and transmitting valid data.

    When using the SFP for the input, do you see a signal at the receiver of the LMH1219? The LOCK_N signal should be going low if it gets a valid input.

    Best,

    Shane

  • 0 in reply to Shane Hauser
    Prodigy 180 points

    Hello,

    Thank you for your reply.

    While we have not personally verified the signal at the LMH1219 receiver end at our company, the board development company has confirmed it.
    I will not mention the name of the board company here, as doing so could affect their reputation.
    The daughterboard used with this Altera FPGA board is equipped with both the LMH1219 and the LMH1218.
    The board development company is conducting a demonstration where the LMH1219 receives an optical SFP signal, and the data is then sent to another board for display.
    Since the image is being displayed, I assume the signal is being successfully captured by the LMH1219; however, even in that demonstration, the LOCK_N signal remained High.
    Additionally, the board development company is not performing a loopback where the signal is fed directly back into the LMH1218.
    I suspect that they are likely using some method to recover and display the (invalid) data obtained while the LMH1219 was in an unlocked state.

    Is my understanding correct that video cannot be displayed if the (invalid) data obtained while the LMH1219 is unlocked is fed directly back into the LMH1218?

    Thank you.

  • 0 in reply to user272328
    TI__Mastermind 38295 points

    Hi,

    user272328 said:
    Is my understanding correct that video cannot be displayed if the (invalid) data obtained while the LMH1219 is unlocked is fed directly back into the LMH1218?

    If the reclocker is bypassed, yes video can still display without a lock. There are a couple checks to narrow this down:

    LOCK_N can be reconfigured as an interrupt pin. Can you confirm the LOCK_N pin is not being reconfigured to a different signal, such as interrupt?

    Furthermore can you confirm that the reclocker is enabled? If the reclocker is disabled it would not lock onto the incoming signal:

    Best,

    Shane

  • 0 in reply to Shane Hauser
    Prodigy 180 points

    Hi,

    First, here are the details regarding the question:

    No specific configuration has been applied to the LMH1219.
    The LOCK_N pin is being used in its default state.

    Regarding the reclocker, the OUT_CTRL pin is left open.

    In light of this, I have two questions.

    Before asking the questions, I will briefly explain the current situation:

    ・With SDI input, LOCK_N goes Low, whereas with SFP input, it goes High.
    ・SDI is connected to IN0; SFP is connected to IN1.
    ・Input data is looped back directly via the FPGA and sent to the LMH1218.
    ・When using SFP input, the SDI output cannot be displayed via the LMH1218.
    ・When SDI input is used, SDI output display is available via the LMH1218.
    ・An Altera evaluation board is being used for the FPGA.
    ・The FPGA is running the unmodified Intel SDI II IP loopback sample design.
    ・Input switching is performed by toggling the IN_OUT_SEL pin between H and L using a jumper.
    ・The OUT_CTRL pin is left open (F), meaning the reclocker is enabled.

    First question:
    The board development company is processing SFP input data under the conditions described above; is it correct to understand that data obtained at LOCK_N is High is incomplete?

    Second question:
    Is it correct to understand that data obtained while LOCK_N is High cannot be displayed as SDI output, if fed directly into the LMH1218?

    Thank you.