RE: [ethmac] rx_ethmac

[yaron4fun@yahoo.com]

Hi,

>From what i know about the ethernet fsm, i think ilan is right about
the sfd and preamble. but in rmii when we detect "11", we should check
that the 3 previos data di-bit where "10", only than we can asume 
that this is the sfd byte

Thanks,
 Yaron

----- Original Message ----- 
From: "Illan Glasner" <iglasner@z... > 
To: <ethmac@o... > 
Date: Mon, 19 Feb 2001 16:44:56 -0800 
Subject: RE: [ethmac] rx_ethmac 

> 
> 
> 17-Feb-01 
> 
>    Hi, 
> 
>       Sorry for the mix word I guess this what happen when you 
> replay 
> and run a netlist check in the same time. 
> 
> Any way back to Premable and SFD the Pre Bye is define as 1010 and 
> 1010 
> and SFD Byte as 1010 and 1101 
> 
> since the first nibble in the SFD is like the nibble of the pre 
> than 
> many time the machine simple look for 1010 and we reffare to it as 
> pre 
> and thn for 1101 and we reffer to it as SFD 
> 
> BUT the MAC need to be able to find at least one nibble of 1010 and 
> than 
> 1101 before deciding that the packet has started. 
> 
> the rest of the preamable byte are need to be checked but not need 
> to be 
> presented and so your test bench need to test for different size of 
> preamable and this have to do with the "shrinking" of the preamable 
> when 
> the packet go through repeters. 
> 
> and so checking only for 1101 can make some mess in your MAC. 
> 
> When it come to transmite than you must generate 7 byte of pre and 
> 1 
> byte of sfd (well for specail purpose in point to point you can 
> reduce 
> this to increase the effective bandwidth, but this is not standart 
> so if 
> you do it make sure it is only an option). 
> 
> in respect to RMII and MII there is no differance between the two 
> the 
> RMII only come to solve pin count problem in high port number chip 
> and 
> the main logic differance is in the behave of rxdv. 
> 
> have a nice day 
> 
>    Illan 
> 
> 
> -----Original Message----- 
> From: Jamil Khatib 
>
[/cgi-bin/post.cgi?cmd=new&to=jamilkhatib75%20at%20yahoo%20dot%20com&msg=/ml-archive/archives/ethmac/0102/msg00009.shtml] 
> Sent: Monday, February 19, 2001 3:34 AM 
> To: ethmac@o...  
> Cc: mgalela@v...  
> Subject: RE: [ethmac] rx_ethmac 
> 
> 
> I do not know exactly what you are talking about but 
> as far as I know that the MAC should detect the 
> preamble and SFD and it should generate them on the 
> transmit side. 
> The whole bytes should be generated and checked 
> These notes are available at least on the MII and RMII 
> interfaces 
> 
> Regards 
> Jamil Khatib 
> 
> --- Mahmud Galela <mgalela@v... > wrote: 
> > 
> > 
> > I wonder what you are thinking about preamble and 
> > SFD (not 
> > SDF...just kidding) pattern. 
> > From previous e-mail (long time ago) i concluded 
> > that the SFD nibble can 
> > come from phy without preceeded by 1010. 
> > It means SFD can be located at first nibble or 
> > second niblle in a byte of 
> > data. 
> > 
> > 
> > 
> > Thanks 
> > 
> > 
> > Mahmud 
> > 
> > 
> > 
> > On Tue, 13 Feb 2001, Illan Glasner wrote: 
> > 
> > > 13-Feb-01 
> > > 
> > >    Hi, 
> > > 
> > > 	I belive your SDF detect is somewhat wrong. 
> > > 
> > > as soon as you see rxdv you start to look for SDF 
> > > 
> > > and your SFD is when you see 1101 
> > > 
> > > BUT the std specify SDF as both 0101 AND 1101 
> > togther and not only the 
> > > second nibble. 
> > > 
> > > this mean unless I'm mistaken and do correct me if 
> > I missed soemthing 
> > > but that if the packet come with let say junk 
> > nibble and one of the junk 
> > > nibble have 1101 than you machine will thing it is 
> > a real packet and 
> > > will start reading it. 
> > > 
> > > more over you might be not align as the 1101 might 
> > come in the first 
> > > nibble and not the second one. 
> > > 
> > > have a nice day 
> > > 
> > >    Illan 
> > 
> 
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