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Ethernet Control and Status registers
366
NS9750 Hardware Reference
Station Address Filter register
Address: A060 0500
The Station Address Filter register contains several filter controls. The register is
located in the station address logic (see "Station address logic (SAL)" on page 321).
All filtering conditions are independent of each other. For example, the station
address logic can be programmed to accept all multicast frames, all broadcast
frames, and frames to the programmed destination address.
Register bit assignment
Register Hash Tables
The MAC receiver provides the station address logic with a 6-bit CRC value that is the
upper six bits of a 32-bit CRC calculation performed on the 48-bit multicast
destination address. This 6-bit value addresses the 64-bit multicast hash table
created in HT1 (hash table 1) and HT2 (hash table 2). If the current receive frame is a
multicast frame and the 6-bit CRC addresses a bit in the hash table that is set to 1,
the receive frame will be accepted; otherwise, the receive frame is rejected.
Bits Access Mnemonic Reset Description
D31:04 N/A Reserved N/A N/A
D03 R/W PRO 0 Enable promiscuous mode; receive all frames
D02 R/W PRM 0 Accept all multicast frames
D01 R/W PRA 0 Accept multicast frames using the hash table
D00 R/W BROAD 0 Accept all broadcast frames
Table 225: Station Address Filter register
Reserved
PRO BROAD
13121110987654321015 14
31 29 28 27 26 25 24 23 22 21 20 19 18 17 1630
Reserved PRM PRA