Re: [802.3_10SPE] MII TX_ER and 10 Mb/s operation

[Yong Kim <yongkim.mail@xxxxxxxxx>]

For 10 Mbps, the referenced behavioral compatibility is with AUI (PLS), which does not have any analog of TX_ER.  So TX_ER must be a 'no op" for 10 Mbps, if MII is used.   And among the motivations of adding TX_ER for 100 Mbps, signalling TX FIFO underrun to assure (corrupted) TX with bad FCS of one of the major ones. 

best regards,

Yong Kim, affiliation: NIO

On Sun, May 6, 2018 at 4:27 PM, Piergiorgio Beruto <piergiorgio.beruto@xxxxxxxxxxxxxx> wrote:

Hello 802.3cg,

while in the process of reviewing comments resolution to draft 1.2, I've stepped into the following possible issue:

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22.2.2.5 TX_ER (transmit coding error) TX_ER shall transition synchronously with respect to the TX_CLK. When TX_ER is asserted for one or more TX_CLK periods while TX_EN is also asserted, the PHY shall emit one or more symbols that are not part of the valid data or delimiter set somewhere in the frame being transmitted. The relative position of the error within the frame need not be preserved. Assertion of the TX_ER signal shall not affect the transmission of data when a PHY is operating at 10Mb/s, or when TX_EN is deasserted.

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So, according to this sentence we should remove support for TX_ER handling from both 10BASE-T1S and 10BASE-T1L.

However I wonder why TX_ER is not to be used in 10 Mb/s mode. I strongly suspect this has historical reasons (any thoughts?)

Eventually, If we find out that there are no real reasons to keep this 'shall' for 10BASE-T1, we may evaluate to keep TX_ER handling and amend clause 22 instead.

Hopefully someone in the group has an opinion to share?

Thank you,

Kind Regards,

Piergiorgio

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