RE: [ethmac] MAC frame memory

["Zhang, Chun Lin (Arnold)" <zhangcl@agere.com>]

> ----------
> From: 	wilton@mail.usa.com[SMTP:wilton@mail.usa.com]
> Reply To: 	ethmac@opencores.org
> Sent: 	2002Äê4ÔÂ4ÈÕ 11:19
> To: 	ethmac@opencores.org
> Subject: 	RE: [ethmac] MAC frame memory
> 
> Hi,
> 
> Thanks your kind reply. I would appreciate very much could you help to 
> clarify my following doubts:
> 1. Is the MrxClk (clock from PHY device) available all the time even 
> without transmission activities? How to keep the local PHY clock from 
> drifting?
> 2. Is the PAUSE timer value assigned by MAC client? How the client 
> know exactly how much PAUSE time it needed?
> 
Yes, PAUSE timer value is assigned by MAC client, but it doesn't matter what
the actual value is. You can just use the maximum value, because you can
clear it by sending a XON frame.

> 3. Is the MAC client always implemented in software?
> Could you refer me some text on the implementation of MAC client?
> Best regards
> 
> Wilton
> 
> 
> 
> ----- Original Message ----- 
> From: "Igor Mohor" <igorm@o... > 
> To: <ethmac@o... > 
> Date: Wed, 3 Apr 2002 13:01:01 +0200 
> Subject: RE: [ethmac] MAC frame memory 
> 
> > 
> > 
> > Thanks, Illan. 
> > 
> > my problem is that ethernet MAC is part of a big system (all cores 
> > are 
> > connected through the wishhbone bus). I don't have bus avaliable 
> > all the 
> > time so I need some memory to hold few words to prevent underrun 
> > and 
> > overrun. 
> > At the end the whole design will be put into ASIC where wishbone 
> > bus will 
> > run at high frequency and bus will be avaliable to Ethernet MAC 
> > almost 
> > all the time. At this moment the design is implemented in FPGA and 
> > wishbone 
> > is running at 25 MHz. Since there are also VGA, RISC, UART, etc. in 
> > the 
> > design, I need some reserve to avoid underrun/overrun. 
> > 
> > Regards, 
> > 	Igor 
> > 
> > 
> > 
> > 
> > > -----Original Message----- 
> > > From: owner-ethmac@o...  
> > [/cgi-bin/post.cgi?cmd=new&to=owner-ethmac%20at%20opencores%
> 20dot%20org&msg=/ml-archive/ethmac/msg00003.shtml 
> > > Behalf Of Illan Glasner 
> > > Sent: 2. april 2002 20:26 
> > > To: ethmac@o...  
> > > Subject: RE: [ethmac] MAC frame memory 
> > > 
> > > 
> > > 
> > >    Hi, 
> > > 
> > > 	Obviusly there are many reason to make all kind of sizes of 
> > > fifo but assuming you don;t plan on having a full packet 
> > stored 
> > > than 5 nibble is enough to compensate for the PPM and even 
> > this 
> > > inculde large margin. 
> > > 
> > > The PPM "effect" is about half nibble so if you start reading 
> > > from the fifo when it have reach the middle you have 2 nibble 
> > > margin in each side which is about 4 time the max requirment 
> > PPM. 
> > > 
> > > Since 5 nibble are only 20 FF you can save a memorey and use 
> > it 
> > > for other place where you might need large memorey or any 
> > other 
> > > use you might have or maybe even be able to use smaller 
> > device. 
> > > 
> > > have a nice day 
> > > 
> > >    Illan 
> > > 
> > > 
> > > -----Original Message----- 
> > > From: Igor Mohor 
> > [/cgi-bin/post.cgi?cmd=new&to=igorm%20at%20opencores%20dot%
> 20org&msg=/ml-archive/ethmac/msg00003.shtml] 
> > > Sent: Monday, April 01, 2002 11:48 PM 
> > > To: ethmac@o...  
> > > Subject: RE: [ethmac] MAC frame memory 
> > > 
> > > 
> > > You're wrong. There are two fifos in the MAC (for transmit and 
> > receive 
> > > frames). 
> > > At the moment each is 8 words big (will probably be changed to 
> > 16). 
> > > Transmit starts as soon as the tx fifo is full. As soon as 
> > there 
> > > is space in 
> > > the fifo for additional word, it is filled up immediatelly. 
> > > 
> > > When receiving frames: as soon as there is at least one word 
> > in the fifo 
> > > it's 
> > > transferred to the memory. 
> > > 
> > > I'm changing the design right now to use bursts and to be able 
> > to use 
> > > non-alligned 
> > > memory to store/load data. It's finished but I have troubles 
> > with the 
> > > implementation. 
> > > 
> > > Regards, 
> > > 	Igor 
> > > 
> > > 
> > > > -----Original Message----- 
> > > > From: owner-ethmac@o...  
> > [/cgi-bin/post.cgi?cmd=new&to=owner-ethmac%20at%20opencores%
> 20dot%20org&msg=/ml-archive/ethmac/msg00003.shtml 
> > > > Behalf Of wilton@m...  
> > > > Sent: 29. marec 2002 12:56 
> > > > To: ethmac@o...  
> > > > Subject: [ethmac] MAC frame memory 
> > > > 
> > > > 
> > > > Hi, 
> > > > 
> > > > I'm new in network and trying to understand this MAC 
> > controller. I was 
> > > > wondering why there is no memory to store the ethernet 
> > frame in the 
> > > > MAC controller. It seems to me that if the host want to 
> > send out a 
> > > > frame, it just transfer the frame to the controller 32 
> > bits by 32 
> > > > bits. Am 
> > > > I right? If it is, how can the MAC controller ensure to 
> > transmit 
> > > > the whole 
> > > > frame continually if there is no frame memory in it? 
> > > > 
> > > > Any comments in this regard are highly appreciated. 
> > > > 
> > > > wilton 
> > > > 
> > > 
> > > 
> > > 
> > > 
> > 
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