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Ethernet Media Access Controller (EMAC) Registers
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5.37 MAC Hash Address Register 1 (MACHASH1)
The MAC hash registers allow group addressed frames to be accepted on the basis of a hash function
of the address. The hash function creates a 6-bit data value (Hash_fun) from the 48-bit destination
address (DA) as follows:
Hash_fun(0)=DA(0)
Hash_fun(1)=DA(1)
Hash_fun(2)=DA(2)
Hash_fun(3)=DA(3)
Hash_fun(4)=DA(4)
Hash_fun(5)=DA(5)
XOR
XOR
XOR
XOR
XOR
XOR
DA(6) XOR DA(12) XOR DA(18) XOR DA(24) XOR DA(30) XOR DA(36) XOR DA(42);
DA(7) XOR DA(13) XOR DA(19) XOR DA(25) XOR DA(31) XOR DA(37) XOR DA(43);
DA(8) XOR DA(14) XOR DA(20) XOR DA(26) XOR DA(32) XOR DA(38) XOR DA(44);
DA(9) XOR DA(15) XOR DA(21) XOR DA(27) XOR DA(33) XOR DA(39) XOR DA(45);
DA(10) XOR DA(16) XOR DA(22) XOR DA(28) XOR DA(34) XOR DA(40) XOR DA(46);
DA(11) XOR DA(17) XOR DA(23) XOR DA(29) XOR DA(35) XOR DA(41) XOR DA(47);
This function is used as an offset into a 64-bit hash table stored in MACHASH1 and MACHASH2 that
indicates whether a particular address should be accepted or not.
The MAC hash address register 1 (MACHASH1) is shown in Figure 76 and described in Table 74.
Figure 76. MAC Hash Address Register 1 (MACHASH1)
31
16
MACHASH1
R/W-0
15
0
MACHASH1
R/W-0
LEGEND: R = Read only; R/W = Read/Write; -n = value after reset
Table 74. MAC Hash Address Register 1 (MACHASH1) Field Descriptions
Bit
31-0
Field
MACHASH1
Value
0-FFFF FFFFh
Description
Least-significant 32 bits of the hash table corresponding to hash values 0 to 31. If a hash
table bit is set, then a group address that hashes to that bit index is accepted.
5.38 MAC Hash Address Register 2 (MACHASH2)
The MAC hash address register 2 (MACHASH2) is shown in Figure 77 and described in Table 75.
Figure 77. MAC Hash Address Register 2 (MACHASH2)
31
16
MACHASH2
R/W-0
15
0
MACHASH2
R/W-0
LEGEND: R = Read only; R/W = Read/Write; -n = value after reset
Table 75. MAC Hash Address Register 2 (MACHASH2) Field Descriptions
Bit
31-0
116
Field
MACHASH2
Value
0-FFFF FFFFh
Description
Most-significant 32 bits of the hash table corresponding to hash values 32 to 63. If a hash
table bit is set, then a group address that hashes to that bit index is accepted.
Ethernet Media Access Controller (EMAC)/Management Data Input/Output
(MDIO)
SPRUFI5B – March 2009 – Revised December 2010
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