We have detected your current browser version is not the latest one. Xilinx.com uses the latest web technologies to bring you the best online experience possible. Please upgrade to a Xilinx.com supported browser:Chrome, Firefox, Internet Explorer 11, Safari. Thank you!

AR# 18371

Virtex-II Pro RocketIO, Ethernet - Is there a maximum Ethernet preamble when using CRC?


General Description: 

Is there a maximum preamble length for Ethernet packets when using the CRC feature of the RocketIO? How is the start of the CRC delimited?


The IEEE 802.3 Ethernet specification specifically states that the preamble is 7 bytes long. Once the CRC circuitry detects the start of packet character (/S/, /K27.7/), it knows a frame is coming and starts a counter. If it does not see the start of frame delimiter (D5) within the first 8 bytes (this is true when the user extended the preamble), it will flag an error. Thus, the start of frame delimiter initiates the CRC computation.

AR# 18371
Date Created 09/03/2007
Last Updated 05/16/2014
Status Archive
Type General Article