The following figure shows the translation of GMII encoding into the code-group stream performed by the PCS Transmit Engine. This stream is transmitted out of the core, either serially using the device-specific transceiver or in parallel across the TBI.
In response to the deassertion of gmii_tx_en, an End of Packet code
group /T/ is immediately inserted. The even and odd alignment described in Start of Frame Encoding persists throughout the Ethernet frame. If the /T/
character occurs in the even position (the frame contained an even number of bytes
starting from the /S/ character), then this is followed with a single Carrier Extend
code group /R/. This allows the /K28.5/ character of the following Idle code group to be
aligned to the even position.