Keywords: GTX, SATA, Serial ATA, beaconing, OOB, elecidle, COMRESET, COMWAKE, COMINIT, RocketIO
When exiting from an electrical idle state following a SATA Beaconing operation (either COMWAKE or COMRESET/COMINIT), the TX serial pins will output 2 extra K28.5 characters before transitioning to TXDATA. The Virtex-6 GTX outputs 4 extra characters.
While this behavior has been observed, it is not expected to cause any problems with a SATA link partner. The SATA specification does not indicate what characters need to be immediately transmitted upon exit from electrical idle, and since 2 consecutive K28.5 characters cannot be recognized as ALIGNp primitives, there is no concern over the misinterpretation of these characters.
To limit the number of K28.5 characters transmitted to a single character, bit 0 of the TX_IDLE_DELAY attribute can be set to 1. The only applies to the Virtex-5 GTX.