MAC Hash Address Register 1 MACHASH1 | Texas Instruments TMS320C674X

5.37 MAC Hash Address Register 1 (MACHASH1)

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EMAC Module Registers

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) XOR DA(6) XOR DA(12) XOR DA(18) XOR DA(24) XOR DA(30) XOR DA(36) XOR DA(42); Hash_fun(1)=DA(1) XOR DA(7) XOR DA(13) XOR DA(19) XOR DA(25) XOR DA(31) XOR DA(37) XOR DA(43); Hash_fun(2)=DA(2) XOR DA(8) XOR DA(14) XOR DA(20) XOR DA(26) XOR DA(32) XOR DA(38) XOR DA(44); Hash_fun(3)=DA(3) XOR DA(9) XOR DA(15) XOR DA(21) XOR DA(27) XOR DA(33) XOR DA(39) XOR DA(45); Hash_fun(4)=DA(4) XOR DA(10) XOR DA(16) XOR DA(22) XOR DA(28) XOR DA(34) XOR DA(40) XOR DA(46); Hash_fun(5)=DA(5) XOR 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 75 and described in Table 74.

Figure 75. MAC Hash Address Register 1 (MACHASH1)

MACHASH1

R/W-0

LEGEND: R/W = Read/Write; -n= value after reset

Table 74. MAC Hash Address Register 1 (MACHASH1) Field Descriptions

Bit	Field	Value	Description

31-0	MACHASH1	0-FFFF FFFFh	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 76 and described in Table 75.

Figure 76. MAC Hash Address Register 2 (MACHASH2)

MACHASH2