Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [ethernet]

Questions about the electrical implementation of Ethernet; ask another Stack Exchange for software or protocol questions. Specify the speed as 10/100BASE-T is somewhat different from 1000BASE-T, apart form the speed. Those are copper standards; Ethernet over fiber optical cable is also defined.

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Why Are Ethernet/RJ45 Sockets Magnetically Coupled?

As the title says really, why do ethernet sockets need to be mag-coupled? I have a basic understanding of electronics, but mostly, I can't figure out the right search terms to google this properly.
slugonamission
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Very long distance Ethernet connection for internet and other data (2000 feet)

I am building a house. It's located about 2000 feet away from the nearest internet cable. I had to run our electrical service underground the whole way, and have already installed a conduit for internet/phone cables from end to end with pull points…
Ryan Griggs
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Connecting two Ethernet PHY without magnetics?

In a (tentative) new design I want to connect two 100 Mbit/s Ethernet PHY similar to LAN8270a, separated by few inches on the same PCB, with same ground plane (but different power supplies). I have the choice of one of my PHY, but the other is…
fgrieu
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What are the 49.9 ohm resistors for in this circuit?

I was wondering what do the 49.9 ohm resistors do in this circuit? Are they absolutely required since I don't have any that size.
Ageis
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ETH PHY Protection during "no supply" condition

My quesiton is simple: In a typical ethernet setup, the RJ-45 jack connects via some transformers (or call it magnetics if you like to) to the Ethernet PHY. (which might be internal to the microcontroll or an external PHY). Now, if the device is not…
Junius
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Is there any way to send serial data over physical ethernet layer with no encapsulation?

I wonder if I can use the physical ethernet layer like a serial port. Is it possible? The case would be reading signals with an electronic device without dealing with networking headers.
Uğur Gümüşhan
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How to increase distance between PHY and RJ45 for GbE?

The PHY I will be using is unfortunately far away from the front panel RJ45 jack (with integrated magnetics). Approximately 13 inches. This is over the maximum recommended distance between the PHY and the magnetics. Is there some sort of a…
cksa361
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Can 64b/66b be forced out of DC balance by malicious data?

Unlike 8b/10b and 64b/67b, 64b/66b relies entirely on the scrambler for ensuring DC balance. This raises the question: can a malicious data stream force the line to leave DC balance? Or would it need access to information that is not exposed by…
Demi
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Center tap of transformer for Ethernet interface

When you see Ethernet PHY chips' application circuit, you can find out the difference about connecting center tap of transformer. Some PHYs should be connect to the DC power but some don't connect to it. The following circuit diagram is for…
Blue Cloud
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Ethernet: What is a jabber timeout

I am writing Ethernet drivers for an STM32 chip. (The reference manual is available here.) At various points, the concept of "jabber timeout" appears, and is not explained. A quick Google search didn't reveal much more information. What is a jabber…
Randomblue
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Reasoning for inverted polarity in center pair of gigabit ethernet (1000BASE-T)

Consider the following table regarding the functions of each wire in 1000BASE-T ethernet (source): For every differential pair except pair C (the blue one, in the center), the white wire is the positive polarity one. Is there any reason for this…
FrancoVS
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10BASE-T1S PHY circuit

In IEEE 802.3cg, a new (2019) 10BASE-T1S interface is defined. The intent is to deliver both power and 10 Mbps Ethernet data over a single conductor pair. I understand 10BASE-T1S was designed to support a very simple PHY front-end implementation. …
Burt_Harris
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Help with Ethernet circuit

To reduce EMI the datasheet recommends using a LP filter as shown in: http://ww1.microchip.com/downloads/en/DeviceDoc/39762f.pdf page 219, Figure 19-2. The filter is made of 56pF capacitor and 120ohm ferrit. Why is the 56pF capacitor placed directly…
JakobJ
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Different recommendations for ethernet front end terminaton?

I’ve noticed different MAC/PHY manufacturers have different recommended termination recommendations for their Ethernet front end. Why does everyone do a variant on the same theme? Does it come down to designer’s preference, or is there a good…
philby
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Lost Ethernet connection with temperature

I have designed an unmanaged Ethernet switch, and cameras that are Ethernet-based with a 100 Mbps connection. If I test my cameras with a commercial switch, they work very reliably up to 60°C or so. If I test the same cameras with my switch I lose…
chourizo
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