Broadcast Address - Sharp LH79524 User Manual

Ethernet MAC Controller
The destination address of received frames is compared against the data stored in the
specific address registers once they have been programmed. The addresses are deacti-
vated at reset or when their corresponding specific address register bottom is written. They
are activated when specific address register top is written, preventing a partial address
from becoming active. If a receive frame address matches, the frame is copied to memory.

6.1.5.1 Broadcast Address

The Broadcast address of 0xFFFFFFFFFFFF is only recognized if the
NETCONFIG:NOBCAST bit is 0. This causes the store frame and the Broadcast
Match Status signal to be sent to the DMA Block.
6.1.5.2 Hash Addressing
The hash address register is 64-bits long and requires two locations in the memory map.
The least significant bits are in HASHBOT and the most significant bits in HASHTOP.
The Unicast Hash Enable and the Multicast Hash Enable bits in the Network Configuration
register enable the reception of hash matched frames. The destination address is reduced
to a 6-bit index into the 64-bit Hash registers. The hash function is an Exclusive OR of
every sixth bit of the destination address:
HASH_INDEX[5] = XOR (DA[5]:DA[11]:DA[17]:DA[23]:DA[29]:DA[35]:DA[41]:DA[47])
HASH_INDEX[4] = XOR (DA[4]:DA[10]:DA[16]:DA[22]:DA[28]:DA[34]:DA[40]:DA[46])
HASH_INDEX[3] = XOR (DA[3]:DA[09]:DA[15]:DA[21]:DA[27]:DA[33]:DA[39]:DA[45])
HASH_INDEX[2] = XOR (DA[2]:DA[08]:DA[14]:DA[20]:DA[26]:DA[32]:DA[38]:DA[44])
HASH_INDEX[1] = XOR (DA[1]:DA[07]:DA[13]:DA[19]:DA[25]:DA[31]:DA[37]:DA[43])
HASH_INDEX[0] = XOR (DA[0]:DA[06]:DA[12]:DA[18]:DA[24]:DA[30]:DA[36]:DA[42])
DA[0] represents the least significant bit of the first byte received, that is, the multicast/uni-
cast indicator, and DA[47] represents the most significant bit of the last byte received.
If the hash index points to a bit that is 1 in the Hash registers, the frame is matched by
whether the frame is multicast or unicast. A multicast match results if the Multicast Hash
Enable bit is 1. DA[0] is 1 and the hash index points to a bit set in the Hash registers.
A unicast match results if the Unicast Hash Enable bit is 1. DA[0] is 0 and the hash index
points to a bit set in the Hash registers.
To receive all multicast frames, program the hash registers with all ones and program the
NETCONFIG:MULTIHASHEN bit to 1.
6.1.5.3 Copy All Frames (Promiscuous Mode)
If the NETCONFIG:CPYFRM bit is 1, all non-error frames are copied to memory. For
example, frames that are too long, too short, have FCS errors or have the ETHERRXER
pin asserted during reception are discarded and all others are received.
6-12 Version 1.0
LH79524/LH79525 User's Guide