Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [phy]

156 questions
15
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Why are Ethernet MAC and PHY separate?

I’ve been looking for a MCU/MPU with built-in Ethernet connectivity, and I’ve noticed that most only contain a built-in Ethernet MAC interface and require an external PHY. Why is this the case, as in why do most of these chips not contain both a MAC…
cdubs
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11
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3 answers

Do all PHY Ethernet chips have a hard-coded MAC address?

For example, this TI PHY chip DP83630 has two MAC addresses that can be used as destination and source MAC addresses for PHY control frames. (page 72 and 94) Does this means all PHY chips will have the same MAC or am I missing something?
Osaid
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11
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2 answers

Ethernet: distance from PHY to magnetics

I am confused as to the preferred placement of Ethernet PHY and magnetics. I thought that in general, the closer the better. But then SMSC/Microchip app note (http://ww1.microchip.com/downloads/en/AppNotes/en562744.pdf) says: SMSC recommends a…
Jan Rychter
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3 answers

Connection of center tap for Ethernet transformer

I'm trying to connect an RJ-45 jack with integrated magnetics (Belfuse L829-1X1T-91 datasheet) to an Ethernet PHY chip (Micrel KSZ8041TL datasheet). The TX+/-, RX+/-, and the LED pins are all easy enough to figure out, but I'm not sure what to do…
pingswept
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9
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Schematic Critique: Phy interface with RJ45/Magnetics

I'm working on my first major schematic design and would really appreciate some feedback on the analog side of the 1000BASE-T Ethernet interface. I'm mostly concerned about the analog line termination and the isolated supply of the analog signals…
stanri
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8
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3 answers

What is the exact difference between SGMII and 1000Base-X?

I was wondering what the exact difference between SGMII and 1000Base-X is, because both seem very similar. Is the "big" difference only the physical medium they are supposed to be transmitted on? Both standards transmit Ethernet frames and use the…
andrsmllr
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8
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DP83848 (Ethernet PHY) 1-bit serial receive data in 10Base-T

Having trouble getting a Texas Instruments DP83848J working in 10BASE-T mode. The link partner and local status register agree that the link is in 10Mbps full-duplex mode. However, instead of receiving 4-bit 2.5Msps data on RXD[3..0] as required by…
Ben Voigt
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7
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1 answer

Design ethernet switch for multiple devices on PCB?

I'm working on a PCB design with a Raspberry Pi CM module and a microcontroller with ethernet capacity. The goal is to connect the devices to the internet. I'm currently using a normal ethernet switch, where I connect the CAT5e cables to the…
pascal0312
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7
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1 answer

Why are there different Ethernet PHY magnetic configurations?

I'm looking at pcb-mount Ethernet ports like these: I'm seeing a few different configurations of the magnetics within the ports. On a single Wurth data sheet, there are 4: Schematic 2 is the part we currently use, but is going obsolete. I found…
Dave
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6
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3 answers

Ethernet 100 ohm differential pair layout

I'm finishing off the layout of a board in Eagle which has a LAN8710A 100Mbps Ethernet PHY on it. The SMSC documentation is really pretty good but I'm stuck on the important detail of how to do the 100\$\Omega\$ differential pairs for the Rx/Tx. I…
Redeye
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6
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2 answers

Media Independent Interface (MII) vs Media Dependent Interface (MDI)

Is my understanding about Ethernet - MII & MDI correct? MII - Media Independent Interface is about the connectivity between MAC and PHY. In other words, it is about TXD and RXD signals from MAC to PHY. MDI - Media Dependent Interface is about the…
V V Rao
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5
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1 answer

What ferrite for Ethernet Phy?

I'm using a Micrel KSZ8051 Phy in a 100mbps design. The datasheet specifies that it should have a small ferrite bead feeding the power. However, the datasheet doesn't suggest any specifications for the ferrite. What should I consider when choosing…
Rocketmagnet
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5
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Connecting a PHY to another PHY on a same board

I would like to connect voltage-mode PHYs with internal terminations back-to-back. After doing some research, it looks like simple AC coupling caps can work, but it's better to use a transformer, especially for 1000baseT. The question is: how do I…
jp28212821
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5
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2 answers

How might an LPDDR2 PHY be designed?

I was reading the LPDDR2 spec today out of curiosity. While browsing the spec I became curious about "how might one hypothetically design a minimal working LPDDR2 PHY on paper/for simulation, perhaps to release as an open source design?" According…
cr1901
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5
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1 answer

RMII MAC side routing and signal integrity

I have some signal integrity and EMC questions. In my board LPC1768 RMII interface is connected to LAN8720. Because of pin locations some RMII signals must go through bottom layer. This is a four layer board, 2nd layer is GND, 3rd layer is Power. I…
zenprogrammer
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