TLK2541 K characters' setting --- full speed & half speed

Here is some feedback on the question:

The GigEther mode works with the two IDLE codes defined in the Ethernet standard.  These are K28.5,D16.2 and K28.5,D5.6.

The Ethernet standard specifies that K28.5,D5.6 should be sent as the first idle in a burst of idles if the running disparity is + to flip the running disparity to -.  All remaining idles in the burst would be K28.5,D16.2.  If the running disparity was – at the beginning of the burst only K28.5,D16.2 idles should be sent.

A user of the TLK2541 has no way of knowing what the current running disparity is so we included the GigEther mode.  In this mode, the actual idles sent on the serial lines will always follow the rules described above as long as the parallel data is either K28.5,D16.2 or K28.5,D5.6.  It really doesn’t matter which of these two D codes is sent since the TLK2541 will always choose the correct one based on current running disparity.  I would choose K28.5,D16.2.

If the customer is using the GigEther mode in full rate they can set TXD[17:0]=18’b01_01010000_10111100.

In half rate mode, the idle is still composed of two bytes that need to be interleaved on the TXD bus.  TXD[16,7:0] needs to alternate between 9’b110111100 and 9’1101010000 with 9’b110111100 always being sent first because the K28.5 must always be in the LSB position of a compliant data stream.

-Atul