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Re: [802.3ae] PMA Loopback

Burt Christian wrote:

> According to table 51-8, transmit source clock specifications for
> fPMA_TXCLK_SRC are +/-100 ppm (or 200 ppm, if you like) for 10GBASE-R
> and +/-20 ppm (or 40 ppm) for 10GBASE-W. And according to table 51-12,
> receiver clock specifications for fPMA_RX_CLK are +/-100 ppm for both
> 10GBASE-R and 10GBASE-W.
> I am trying to understand why you mentioned 120ppm for 10GBASE-W ?

This assumes that the 10GBASE-W is transmitting 20ppm too fast (for
instance) and that the receiver is recovering a signal which is 100ppm
too slow. While both the Tx and Rx are in spec, the delta is 120ppm.
My key point was that there are frequency differences which would
have to be compensated for, and the PMA/PMD has no way to perform
this compensation (as specified).

Tim Warland  P. Eng.
Applications Engineer
Quake Technologies   (613)270-8113 ext 2311

The secret of happiness is freedom, and the secret of freedom is courage.