Ethernet Controller EC1_GTX_CLK125 pin

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Ethernet Controller EC1_GTX_CLK125 pin

4,167 Views
Ellu24
Contributor III

Hi

I am designing a hardware using LS1046 and I want to connect ethernet PHY VSC8502-03 , which uses RGMII MAC interface, so that I have to connect that to EC module of processor. My questions are: 

1) what should I connect to EC1_GTX_CLK125 pin( any external crystal or clock generator Si 5332 output or any pins from ethernet PHY)

2)If I am not using EC2 , Can I left it unconnected?

3) Should I use synchronous ethernet as specified in VSC8502-03 datasheet, where should I connect RCVRDCLK1,RCVRDCLK2, CLK_SQUELCH_IN. (I have attached VSC8502-03 datasheet. Please find the attachment) 

Thanks in advance

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6 Replies

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Ellu24
Contributor III

Thank you for the reply. I have one more question that, from PHY VSC8502-03, which pin I should connect to CLK125? PHY datasheet is attached above. Please find the attachment.

 

Thanks in advance.

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yipingwang
NXP TechSupport
NXP TechSupport

#1) I normally recommend to follow the reference design board. The schematics show the CLK125 coming from the PHY. Is this an option for the customer to use their PHY?
#2) Follow the NOT USED recommendations in AN5252, Design checklist.
#3) Only LX2 has SyncE type support.

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icrowe
Contributor I

I have a very similar question about the CLK125 pin.  But the phy I am designing with, Microchip LAN8820i, does not have a CLKOUT pin like the Realtek part referred to in the evaluation board. The two options would appear to be:
1) buffer and share the input clock to the phy, which I generate from a clock chip rather than a crystal or oscillator.
2) buffer and share  the RXC clock from the PHY

Which is correct, or is there a better third choice?

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yipingwang
NXP TechSupport
NXP TechSupport

It all depends on the PHY. The REALTEK PHY we have on the LS1046ARDB has a CLKOUT pin that can be used.
I don't see a similar pin on the VSC device. You might have to check with that PHY vendor to be sure.
I only see a 125MHz input pin called REFCLK. So, if they want to use this PHY, they may have to use the same external clk source to feed the CLK125 input on the LS1046A.

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Ellu24
Contributor III

Thank you very much for the reply. So can I provide 125MHz using external clock generator Si5332? Is this the right connection?

Thanks in advance

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yipingwang
NXP TechSupport
NXP TechSupport

As long as the clock source meets the datasheet requirements, it should work.