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Visitor msagautam
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1,228 Views
Registered: ‎12-17-2017

Ethernet PHY addressing on Zync 7000

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I see that when I poll the 32 different phy addresses, valid contents in registers 2 and 3 indicates that there is a (physical) PHY linked to that phy address. How are these addresses initially assigned to the PHY?

So if I have two PHYs sharing MIO pins 52...53, How does each PHY know its PHY address so that it responds to a particular address? Does connection to MII pins of the MAC assign this address?

How do we know which physical PHY is connected to which MAC in the scenario where we have two PHYs and two MACs sharing one MDIO interface?

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1,780 Views
Registered: ‎01-08-2012

Re: Ethernet PHY addressing on Zync 7000

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It's not possible to tell exactly which Ethernet PHYs you are talking about.  Are they physical PHYs on the PCB?  Are they IP cores in the FPGA fabric?

 

Assuming the former (physical PHY chips on the PCB), there will probably be some strapping pins on the PHY to hardwire the selection of MDIO address.  For example, on an old board of mine I have two Marvell 88E1512 PHYs on the same MDIO.  One has address 0 and the other has address 1.  This is controlled by the connection to the config pin of that device (config pin tied to the "LED1" pin gives address 0 and config pin tied to the "LED0" pin gives address 1).  Please note that the address is determined by the PCB design, not by anything in the Zynq.

Whatever PHYs your board uses will have some way of determining the address.  It will probably be completely different to the one used on the PHYs on my board.  Possibly it will be read from a configuration EEPROM rather than a set of pins.  You will need to read the datasheet for your PHY to find out.

 

Allan

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1,781 Views
Registered: ‎01-08-2012

Re: Ethernet PHY addressing on Zync 7000

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It's not possible to tell exactly which Ethernet PHYs you are talking about.  Are they physical PHYs on the PCB?  Are they IP cores in the FPGA fabric?

 

Assuming the former (physical PHY chips on the PCB), there will probably be some strapping pins on the PHY to hardwire the selection of MDIO address.  For example, on an old board of mine I have two Marvell 88E1512 PHYs on the same MDIO.  One has address 0 and the other has address 1.  This is controlled by the connection to the config pin of that device (config pin tied to the "LED1" pin gives address 0 and config pin tied to the "LED0" pin gives address 1).  Please note that the address is determined by the PCB design, not by anything in the Zynq.

Whatever PHYs your board uses will have some way of determining the address.  It will probably be completely different to the one used on the PHYs on my board.  Possibly it will be read from a configuration EEPROM rather than a set of pins.  You will need to read the datasheet for your PHY to find out.

 

Allan

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Visitor msagautam
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1,186 Views
Registered: ‎12-17-2017

Re: Ethernet PHY addressing on Zync 7000

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Thanks Allan, I must have been clear that I wanted to know about physical PHYs on the PCB. Anyway, you have answered my question. Cheers.

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