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New Member

Detection of a network connection on a switch

Hello

I am currently designing a ethernet driver on PowerPC.

To validate the issue of my ethernet frames, I connected with a crossover cable, my evaluation board to a PC where wireshark is running. This configuration works. The frames are sent and received on the PC. All my frames are displayed on wireshark.

My problem is this.
When I try to connect my board to a switch with an ordinary cable (to send frames to multiple PCs), the switch (a Cisco Catalyst 2950) did not not detect the presence of a connection, the LED is off desperately.
I think I have omitted the management of certain signals in my PowerPC registers settings.

So I have several questions : How does the switch to detect a connection? What signals should be set so that the switch detects the line?

In advance thank you.

PS: The connection is configured for full duplex 100M.

3 REPLIES

Re: Detection of a network connection on a switch

Hello

I am currently designing a ethernet driver on PowerPC.

To validate the issue of my ethernet frames, I connected with a crossover cable, my evaluation board to a PC where wireshark is running. This configuration works. The frames are sent and received on the PC. All my frames are displayed on wireshark.

My problem is this.
When I try to connect my board to a switch with an ordinary cable (to send frames to multiple PCs), the switch (a Cisco Catalyst 2950) did not not detect the presence of a connection, the LED is off desperately.
I think I have omitted the management of certain signals in my PowerPC registers settings.

So I have several questions : How does the switch to detect a connection? What signals should be set so that the switch detects the line?

In advance thank you.

PS: The connection is configured for full duplex 100M.

Hi,

There are two types of link pulse signal is used to inform a “link partner” that a new station is on the line and that it is seeking to establish a connection.These two versions of link pulse are Normal Link Pulse (NLP) and Fast Link Pulse (FLP).

The 10BASE-T link pulse (the NLP) consists simply of a half-wave pulse, transmitted eight times per second on the TX pair whenever data is not being sent. Data signals are from +1 to -1 volts.When Fast Ethernet was developed,they selected the simplest mechanism available for negotiating which physical signaling system and configuration to use.

The FLP burst relies upon the presence or absence of NLPs in a certain order to communicate a binary word where each bit position represented a particular link ability. Fast Link Pulse bursts are implemented using NLPs, but as a burst of pulses that contains all of the information about the connecting device’s speed and duplex capabilities

So an ethernet link can use auto negotiation as it  permits more than one FLP link word to be exchanged, and for some configurations, there could easily be three or four different FLP link words sequentially exchanged.

Hope to help !!

Ganesh.H

Cisco are currently donating money to the Haiti earthquake appeal for every rating so please consider rating all helpful posts.

New Member

Re: Detection of a network connection on a switch

Hello

First, thank you for these informations. They have been very helpful, but despite various  manipulations concerning modes of negotiation on my PHY interface, LEDs stay off  on my CISCO switch.


So I tried to  connect my PHY to another switch that I've keeped on hand (a small "HP procurve switch 408"),  and I succeed in getting a working connection.
It could miss something in the setup of my CISCO switch.


So I need some  anothers informations.
For a switch  port, what do
the  possibles states of the LED (Off, Orange and  Green) mean?
What triggers the activation of the Orange LED?

What kind of differences (in terms of psysical interface) exists between an HP switch and a CISCO catalyst 2950?

Thanks in advance.

Ptit

New Member

Re: Detection of a network connection on a switch

Hello (again)

I finally succeeded to solve my problem. The  problem was the "scrambler" function which was bypassed on the PHY interface.

I add some informations about the scrambler :


The scrambler is required to control the radiated emissions (EMI) by spreading the transmit energy across the frequency spectrum at the media connector and on the twisted pair cable in 100Base-TX operation.
By scrambling the data, the total energy presented to the cable is randomly distributed over a wide frequency range. Without the scrambler, energy levels on the cable could peak beyond FCC limitations at frequencies related to repeated 5B sequences like continuous transmission of IDLE symbols. The scrambler output is combined with the NRZ 5B data from the code group encoder via an XOR logic function. The result is a scrambled data stream with sufficient randomization to decrease radiated emissions at critical frequencies. 

This is an extract of my PHY interface documentation (DAVICOM DM9161).

Thank you for your help.

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