User Manual

UM10360 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2010. All rights reserved.
User manual Rev. 2 — 19 August 2010 212 of 840
NXP Semiconductors
UM10360
Chapter 10: LPC17xx Ethernet
For hash filtering, this function is passed a pointer to the destination address part of the
frame and the CRC is only calculated on the 6 address bytes. The hash filter uses bits
[28:23] for indexing the 64-bits { HashFilterH, HashFilterL } vector. If the corresponding bit
is set the packet is passed, otherwise it is rejected by the hash filter.
For obtaining the destination and source address hash CRCs, this function calculates first
both the 32-bit CRCs, then the nine most significant bits from each 32-bit CRC are
extracted, concatenated, and written in every StatusHashCRC word of every fragment
status.