DP83848Q-Q1: I need a 100Mb RMII phy that will be compatible with network controller NC-SI/RMII sideband

Hi,

I have an application where I need a phy to interface with a Network Controller (NC) which has a NC-SI/RMII sideband.  Since both phy and NC have the same orientation for inputs/outputs, as per Table 119 (page 131) of this spec

https://www.dmtf.org/sites/default/files/standards/documents/DSP0222_1.1.1.pdf

the phy and NC must be connected in a crossover (back-to-back, repeater, etc)  fashion. The NC will not know there is a phy connected in this manner though, any adjustments to make communication work must be made in the phy configuration

From the RMII spec 1.2, there are differences between transmit and receive that make the signals not easy to cross-over.  CRS_DV is not co-incident with the Preamble in RXD, and there can be toggling at the end.  TX_EN is co-incident with the Preamble in TXD, and there is no toggling.

http://ebook.pldworld.com/_eBook/-Telecommunications,Networks-/TCPIP/RMII/rmii_rev12.pdf

5.3.1 RXD[1:0] in 100 Mb/s mode
For normal reception following assertion of CRS_DV, RXD[1:0] shall be “00” until the
receiver has determined that the receive event has a proper Start of Stream Delimiter.
Thereafter, preamble will appear (RXD[1:0]=01). Data capture by MACs occur following detection of SFD.

5.4 TX_EN
Transmit Enable
TX_EN indicates that the MAC is presenting di-bits on TXD[1:0] for transmission.
TX_EN shall be asserted synchronously with the first nibble of the preamble and shall
remain asserted while all di-bits to be transmitted are presented.

I see that dp83848q-q1 and several other phys that I check will allow the use of RX_DV instead of CRS_DV in the path from phy to NC.  I think this solves the problem of transmit from phy to NC, NC will basically receive what it normally gets on TXEN/TXD.

My question is about the transmit path from NC to phy though, the phy would need to accept basically a CRS_DV signal, or perhaps a CRS_DV that has CRS removed, but still the data will be 00 when CRS_DV asserts, it will not the preamble that is usually expected with TX_EN.  Are there any phys that can be configured to be compatible with, and receive, CRS_DV/RXD on their TXEN/TXD lines ?

Thanks...