AR# 33155

Virtex-5/6 GTX Transceiver - SATA Beaconing may transmit 2 or 4 extra characters upon exit of electrical idle


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. 

This only applies to the Virtex-5 GTX.

Linked Answer Records

Associated Answer Records

Answer Number Answer Title Version Found Version Resolved
33475 Virtex-6 FPGA GTX Transceiver - Known Issues and Answer Record List N/A N/A
AR# 33155
Date 05/18/2015
Status Active
Type General Article
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