Stack Exchange Network

Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit 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.

0
votes
2answers
120 views

60Hz Ethernet Wave?

I just unsheathed an Ethernet cable and probed it with a scope. What I see is an almost perfect 60Hz sine wave signal. Why is this? I can't find anything that would explain to me why this is the case. ...
1
vote
1answer
233 views

Should I remove terminating resistors in ethernet TAP?

I would like to design Ethernet TAP, with PHY, that I can connect to FPGA via RGMII interface. I know, that I could do this like there, but I would like to be able to analyze low level data in MAC. ...
0
votes
1answer
109 views

Poor bandwidth after re-coupling an Ethernet cable

As part of an experiment I cut a Cat 5e Ethernet cable in half, stripped off a small amount of insulation on each wire and attached each pair of wires together with its own alligator clip. There are ...
1
vote
3answers
684 views

Ethernet Magnetics Required? [duplicate]

I'm currently developing a device which require an ethernet switch on it (to provide Internet connection to a microprocessor and an iPad). One of the major goal is to make it very small. I found an ...
1
vote
1answer
1k views

Does SGMII use MDIO?

I was reading the SGMII specification and the documentation of a Gigabit MII to SGMII converter (see MAX24287). I do not see a MDIO to control the registers of the PHY (Basic Mode Status Register, ...
0
votes
2answers
424 views

Was Ethernet ever bidirectional over a single coaxial cable or single twisted-pair line?

Comments below this answer to the question Why was SpaceWire designed with nine wires? involve the history of Ethernet. Did the earliest forms of Ethernet allow complete bidirectional communication ...
0
votes
1answer
411 views

Using unshielded RJ45 with shielded Cat6 in a server cabinet

I'm about to do cabling in a server rack that consists of two switches and forty 1U servers. Since every server has three ethernet cables attached we'll have around 120 cables in a single rack. Is ...
0
votes
3answers
405 views

Scrambler with all zeros on input

Several communications standards use LFSR-based self-synchronizing (multiplicative) scramblers that are never reset to an initial state after initial power on. For example, 10GBASE-R Ethernet ...
2
votes
1answer
783 views

Connect STM32 Ethernet to PHY - clock signal

I want to connect MAC available on STM32F745 to KSZ8041FTL (PHY) via RMII. I will clock PHY from external 50MHz clock generator, connecting clock to the REFCLK input of PHY. But what about STM32? ...
2
votes
1answer
3k views

standard ethernet pinout for M12 A coded

I would love to follow the most common pinout (I design connector and receptable, but you never know). I find conflicting sources: -RJ45 connector exact same pinout number by number: -A big cable ...
1
vote
2answers
160 views

Detect activity on RJ45

I would like to make a circuit that allows to detect activity on a RJ45 cable (on which Ethernet would be used). When the cable is only connected to a single computer, link test pusles are emitted. ...
2
votes
2answers
242 views

How many segments are permitted in CAT 6A cable run?

How many segments are permitted in an F/UTP CAT 6A cable run? Segment endpoints require peeling back the foil and untwisting the pairs, which I fear will affect data speeds. I heard that a cable run ...
41
votes
10answers
24k views

Why is an Ethernet cable not grounded?

There is no dedicated GND in the classical Ethernet 8P8C ("RJ45") pinout.[1] Why does the Ethernet spec not include a ground, unlike many other cable types used for interconnecting devices that may ...
2
votes
1answer
693 views

Marvell PHY to KS8999 PHY connection

I'm trying to design a custom board with Marvell 88E1111 PHY and I want to connect this board to another board with KS8999 PHY on it. I want to connect two phy sides with capacitive coupling. The ...
1
vote
1answer
149 views

Unidirectional PHY transceiver

I am trying to establish a unidirectional connection over a RJ45 cable (not an optical fiber). I saw in the IEEE 802.3 standard that the clause 66 describe how unidirectionnal chips should work. ...
6
votes
1answer
513 views

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 ...
0
votes
1answer
274 views

Establishing a physically enforced unidirectional Ethernet link with 1000BASE-X, fiber optic PHY

I have a use case where I am attempting to establish a unidirectional Ethernet link where a singular fiber is used to transmit data to the receiver. The Rx of the transmit side and the Tx of the ...
-1
votes
1answer
285 views

LG TV RS232 Control over rollover cable [closed]

My LG TV can be controlled over a RS232 port! The Problem is that I don't have any serial devices to test it. So my question is, can I do it with a rollover cable(RJ45 <--> D9)? I mean can I ...
3
votes
2answers
783 views

What are the NAND Trees that Ethernet datasheets refer to?

I have read a few Ethernet transceiver datasheets and they always have some short section akin to "NAND Tree Support" or "NAND Tree I/O Testing", and from what I gather from these small bits of ...
2
votes
2answers
2k views

Ethernet Trace Layout with PoE & Integrated Magnetics

I'm a hobbiest & I've put together a simple PoE board using a LinkIt Smart Duo, the AG9050-2BR and a Bel Fuse 0813-1X1T-57-F. The power circuit works but the Ethernet signal wont work. The ...
1
vote
3answers
1k views

Ethernet PHY/MAC/SWITCH IC available?

I'm wanting to use an ethernet switch/Phy LAN9303 to output 2, maybe 3 ethernet signals. I know that I need a 25MHz clock, supporting resistors and caps as well as the magnetics, but I want to know if ...
1
vote
3answers
312 views

Can floating cat6 shield be worse than unshielded?

I'm having an electrician fish an Ethernet cable through a wall. I can put shielded or unshielded cat6. However, the electrician doesn't know how to crimp Ethernet cable so I agreed to do that part ...
-1
votes
1answer
505 views

WiFi physical layer (PHY) for STM32 [closed]

I have a STM32 uC that has an internal Ethernet controller. If I want to use LAN I just buy some cheap PHY chip, RJ45 socket and it works. What If I want Wi-Fi? Is there any chip that can be placed ...
0
votes
1answer
58 views

KSZ8863MLL issue - suggestions on resolving

I have a NXP K64 cpu connected to a KSZ8863MLL (two port Ethernet switch) operating in MII mode. I built 10 boards -- 9 work. The board that does not work properly behaves as follows (testing using ...
1
vote
2answers
1k views

Why are Ethernet jack center taps connected to VCC?

Taking this schematic as an example: EtherTen Can someone explain to me why the center taps of the transformers (TXCT, RXCT) are connected to VCC? I've seen this connection in many (although not all)...
0
votes
1answer
209 views

How to implement serial-to-fiber optic Ethernet with WIZnet W5500? [closed]

I'm using W5500 to implement a serial to Ethernet converter, but I need to transmit over fiber optic cables. I will have a TX cable and a RX cable. How can this be done since the output of W5500 is ...
0
votes
2answers
354 views

Is there an excuse for a 20ft Cat6 Ethernet cable to have 36μH on all wires?

I was just measuring the inductance of the 20ft (6m) Cat 6 Ethernet cable I just bought. I'm aware that 525 nH/m is what's expected for each wire, so that ought to have been 3.15μH. I've measured ...
0
votes
1answer
890 views

How to implement PoE with WIZnet W5500?

I want to implement a PoE solution and I started to design the board based on WIZnet's W5500 reference designs. I am using the design with the external transformer. My questions are: How to adapt ...
2
votes
1answer
1k views

RGMII - Origin of RGMII and does a standard exist?

I'm implementing an Ethernet system on a Xilinx FPGA, and I've been reading IEEE 802.3-2015, but nowhere have I found mention of RGMII which is the interface to the PHY. After extensive searching, I ...
3
votes
3answers
581 views

Why use discrete Ethernet transcievers?

It is common to find microcontrollers with an integrated 10/100 Ethernet MAC and PHY. Some microcontrollers, such as the Texas Instruments TM4C129x series, offer both an integrated PHY and RGMII ...
6
votes
1answer
3k views

How does Ethernet magnetics work?

If you refer to Figure 14 of http://www.analog.com/media/en/technical-documentation/application-notes/EE-269.pdf. There are 2 transformers on each data pair. Can someone help explain how they work? ...
1
vote
2answers
123 views

What technology to use to send data/Ethernet (about 128 kbps) over copper cable (4km)?

What thechnologies can i use to send data/ethernet (w/ a symmetrical traffic throuput of about 128kbps) over copper cable (4km)? 1)SHDSL would be an option !!(but I couldn't find any chip with ...
0
votes
1answer
99 views

How do you determine which ethernet standard I am using?

I am new to the field and learning as a gateway via Ethernet cabling. I was curious as to how exactly these standards were implemented. Are these standards implemented as per the data transfer ...
3
votes
1answer
1k views

Can I use an ethernet jack to send LVDS signals?

I would like to use an Ethernet jack for the form factor and CAT5e+ cable properties (shielded/twisted, characteristic impedance, etc) to send LVDS signals over a long length of cable (100+ ft). When ...
0
votes
1answer
801 views

What do pull-up and pull-down resistors do in an ethernet PHY?

I've noticed that most ethernet physical layers (i.e. the interface between the MAC/network and e.g. an RJ45 connector with magnetics) have pull-up or pull-down resistors on the TX and RX lines. For ...
1
vote
4answers
138 views

electrical circuit contains elements with unique id

I want to build network (electrical circuit) which contains hundreds of elements (with unique IDs) based on some microcontroller. Good example of that kind of network but much more expensive (and ...
0
votes
1answer
1k views

how to interface RS-422 to UART on my MCU? [duplicate]

I'm trying to interface RS-422 data to the UART on my MCU (TM4C1294ncpdt) to send it through its ethernet interface. Can anyone help me with how to convert the RS-422 differential signal to be read ...
5
votes
5answers
5k views

Implement send-only (one-way) Ethernet cable

I want to build a unidirectional comminucation. In transportation layer of this device, it needs a one-way media to send data from side A to side B. All commercial products use SFP. I tested some SFP ...
0
votes
1answer
135 views

Ethernet LEDs won't turn off when i unplug the Ethernet cable

I'm working on a custom board equipped with a Ka-Ro TX28 module and the LAN9500A USB to Ethernet controller without EEPROM for the network interface. Operating system is Linux (Yocto). The LAN9500A is ...
1
vote
1answer
384 views

Dysfunctional onboard LAN controller chip getting very hot, is it safe? [closed]

I have had an Intel LGA775-based motherboard (DG33FB) for about 8 years now, but for an year or so the LAN port was unreliable, sometimes working and sometimes not. No software solution was working, ...
-1
votes
1answer
436 views

IP Camera IC (PAL to Ethernet)

I have a design problem to capture CCIR/PAL video from the camera that is available and send it over ethernet. Need to come up with my own printed circuit board design, having no prior experience in ...
23
votes
3answers
5k views

How does a 40 Gbit/s Ethernet interface process packets in silicon?

A 40 Gbit/s Ethernet interface should have a 40 GHz signal on it. How does common silicon IC technology handle such an exotic beast? My best guess is that internally various parallel busses are used, ...
5
votes
1answer
576 views

Why 3v3 should be connected to the center point of Ethernet termination?

I am designing an 10/100 Ethernet on my board and I can't understand why 3.3V should be connected to the center point of the termination. The schematic checklist recommends it actually and I checked ...
3
votes
1answer
2k views

Stepping down 48V (from power over Ethernet) to 5V

I'd like to use power over Ethernet to power an ATMega328 microcontroller at 5V, however PoE operates at around 48V for commercial PoE switches. How can I drop the voltage from 48V to 5V efficiently? ...
0
votes
2answers
185 views

Design Question: 20 MS/s data acquisition

Let me preface that I am fairly new at working with sampling high speed signals. Specifically, I want to do some processing on slightly corrupt NTSC signals. For this, I need to sample at above 14.3 ...
2
votes
1answer
4k views

What is GMAC/EMAC and does it define a physical connection to an ethernet chip?

Background I'm trying to understand if there is a dedicated protocol that dictates the way CPU on an embedded board is connected to an Ethernet chip. For example if it's some dedicated equivalent to ...
0
votes
1answer
157 views

Double magnetics for ethernet?

I have a main board with a 10/100 MAC and PHY. This board also includes a discrete magnetics. The board is connected via a suitable high speed board-to-board connector to another board, that contains ...
1
vote
2answers
226 views

Negotiation fails on KSZ8895 Micrel Switch IC

Why does the negotiation with the network fail? The only common issue I found is the voltage gets a "load" which drops the pulse peak for a short time. Here negotiation fails: Here negotiation is ok:...
1
vote
1answer
874 views

Ethernet PHY Output Driver stage

Where can I find a basic block diagram with descriptions for a typical 10/100BASE-T PHY output driver stage? I also wonder whether all drivers use "current-mode" outputs that lead to voltage across ...
0
votes
1answer
135 views

Function of a component in a Ethernet Board

I want to know what is the component located next to the Ethernet input for. I guess it is for filtering, but I'd like to know it's name and it's main function if possible. Here it is the board: The ...