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DS50PCI402 auto Rx detection

NAOKI AOYAMA
Guru 11215 points
Other Parts Discussed in Thread: DS50PCI402

Hello,

Our customer use the DS50PCI402, want to know about  the auto Rx detection.

The customer's condition is as follows.

x4 lane
ENRXDET=0 RXDETA/B=0
connecting:ASIC---DS50PCI402---end point device

system sequence is as follows.

pattern A
power on all devices with reset on
PRSNT pin contiue Low fron start
reset removal

patternB
Power on all devices with reset on
PRSNT Low High Low (toggle)
reset removal

In case of pattern A, there's no problem with Link-up.
In case of pattern B, Link-up fail sometime at some lane.

question 1

Is there any difference from pattern A to pattern B with
the auto detection system?

question 2

Does it need 5ms(min) from PRSNT high to Low to reset removal?
(It is mentioned on the datasheet P10 Fig.2.)

It is no problem in the case of the manual detection mode.
But, the end user of the customer decide use or not use the auto Rx detection.
So, the customer have to make the DS50PCI402 to use the auto Rx detection correctly.

Best Regards,

Naoki Aoyama

  • 0
    TI__Mastermind 29635 points
    Hi Aoyama-san,

    1. There may be a difference between Pattern A and B. It depends on how long the PRSNT/ pin is asserted high when you perform the toggle. According to the datasheet, in the case of Pattern B, the PRSNT/ pin must be held high for at least 5 us in order to ensure that the DS50PCI402 undergoes a complete analog power-down. Otherwise, the RXDET functionality may not re-initialize properly.

    2. You will need at least a 5 us (not 5 ms) wait after asserting the PRSNT/ pin high so that the analog in the DS50PCI402 can power down completely.

    Normally, we see customers implement the design where ENRXDET = 0 and RXDETA/B = 0 when the device starts up so that it is immediately in Auto Rx Detection, rather than toggling the PRSNT/ pin. The typical design is to have the PRSNT/ pin connected to a "Power Good" input signal such that the DS50PCI402 PRSNT/ pin is only toggled when the "Power Good" input signal (in other words, the connected device to the DS50PCI402) is removed. Otherwise, the PRSNT/ pin will not be toggled.

    Thanks,

    Michael
  • 0 in reply to Michael Lu (Santa Clara)
    Guru 11215 points
    Hello Michael,

    Thank you for your reply.
    It is showed the PCI system timing on the datasheet P10 Fig.2.
    Does it need 5ms for reset removal of the ASIC and device?

    Best Regards,
    Naoki Aoyama
  • 0 in reply to NAOKI AOYAMA
    TI__Mastermind 29635 points
    Hi Aoyama-san,

    Thanks for clarifying. The 5 ms specification is the recommended amount of time for the DS50PCI402 to become active and stable from a low-power state, which occurs when the PRSNT# pin goes from high to low.

    Regards,

    Michael
  • 0 in reply to Michael Lu (Santa Clara)
    Guru 11215 points
    Hi Michael,

    Thank you for your reply.
    I understood the timing.

    Very Thanks,
    Naoki Aoyama