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Hi Team,
My customer has 2 questions regarding MIDO, could you follow these questions below?
1. Pull-up registers
2.2kohm pull-up register are used on MDIO line though, can they change it to 1kohm?
According to My customer, They have seen bad waveform like below at MDIO lines (TLK10232 to FPGA) on their board. It looks like low pass filter was applied(There may be a relatively large parasitic capacitance on the lines).
2. Meaning of Tvalid indicated in 9.10 MDIO Timing Requirements
My customer want to know what Tvalid means, could you tell me that with a timing chart like Figure 9-4. MDIO Read/Write Timing?
Regards,
Takashi Onawa
Hello Takashi,
How is the MDIO pin of the FPGA configured, and does anything else share the MDIO bus? Typically MDIO is an open-drain I/O, meaning that when it is configured as an output it will either sink current to ground to pull the line low or be high impedance so that the line can be pulled high externally.
Could customer try a ~4.99k pull-up resistor? Even the MDIO specification mentions a pull-up resistor from 1.5K - 10K. In the TLK10232EVM you can find a ~4.02k pull-up resistor populated.
Regarding the Tvalid:
Regards,
Luis Omar Moran
High Speed Interface
Hi Luis-san,
The MDIO line from FPGA is connected to two TLK10232 through connector and 4~5 inch PCB trace. 2.2kohm resister is populated as Pull-up resister on the line. I'm guessing that this is due to parasitic capacitance on MDIO line, and they also estimated that. Anyway, I recommend them to use more slower MDC rate to avoid this issue and they closed this issue ones.
Regarding the Tvalid, Could you tell me the meaning of Tvalid in detail?
I and my customer could not understand the meaning of the Tvalid you showed above.
Also, I and the customer think the Tvalid is defined as MDC down edge to MDIO transaction as below though, Is it really from up edge?
If it was really from up edge, we could not secure its hold time in data read/write transaction in some cases.
If Tvalid means TLK10232's output timing variation on MDIO line, it makes sense for us...
Regards,
Takashi Onawa
Hello Takashi-san,
Sorry for the confusion. The Tvalid is as follows:
Best Regards,
Luis
OK, simple question.
"Tvalid" and "MDIO (output) delay time" shown in the figure below are same parameter, aren't they?
Regards,
Takashi Onawa
