Thread Links Date Links
Thread Prev Thread Next Thread Index Date Prev Date Next Date Index

RE: Gearbox reality check

8b/10b is mutually exclusive of 64b/66b.  The data out of the MAC is 8b/10b
encoded for transmission across the XAUI interface, it is then decoded at
the other end and re-encoded into 64b/66b by the PCS logic.

Clear as mud?


		-----Original Message-----
		From:	Erik Trounce [mailto:erikt@xxxxxxxxxxxxxxxxxx]
		Sent:	Wednesday, June 21, 2000 8:57 AM
		To:	Booth, Bradley
		Cc:	HSSG
		Subject:	RE: Gearbox reality check


		Ben, does this question sound familiar?

		My view of this so far is that without the WIS (i.e. UniPHY
		mode), data coming out on the OIF/SUPI interface is simply
the PCS
		output, albeit at a slightly higher rate.  For example,
		a 16-bit OIF network interface and an XGMII MAC to PCS
		the clock rate on the OIF is 644.53125 MHz, and the data is
66-bit PCS
		codewords, split up 16-bits at a time.

		Now, if you add the XAUI interface between the MAC and PCS
		which includes the 8b/10b encoding, I think you need to go
		faster on the OIF interface (805.6641 MHz!), to maintain 10
		from the MAC.  This can't be right.  Are 8b/10b encoding and
		encoding mutually exclusive?  Or is the 8b/10b encoding only
		across the XAUI interface with the two XGXS interface layers
		encoding/decoding the RS data (MAC sends ethernet, RS
encodes as
		XGMII, XGXS does 8b/10b encoding, sent across XAUI, XGXS
		decodes, PCS receives XGMII data, performs 64b/66b encoding,

		Can anyone clarify?

		Erik Trounce

		In message "Gearbox reality check", Booth, Bradley writes:
		>Gold star!
		>Now, can you explain how it works without the WIS? :-)