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Adapter Internal Registers
A-31
Register Definitions
mode, functional addressing is supported through the general address regis-
ters. If any address register contains a functional address (group/specific = 1;
local/universal = 1; group/functional = 0), that register’s two MSbytes are
compared normally, but its 31 LSBs are compared on a functional bit-match
basis. Any of the registers can be used to hold functional addresses; all the
registers are identical.
In token ring frame format mode, the adapter responds to an additional broad-
cast address: The all-nodes (this ring) broadcast address of
0xC000 FFFF FFFF (but only if the NOBRX bit in the NetCmd register is not
set).
A.3.9 Hash Address Registers–HASH1/HASH2 @ 0x28–0x2C (DIO)
The hash registers allow group-addressed frames to be accepted on the basis
of a hash function of the address. The hash function calculates a six bit data
value from the 48-bit destination address, 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)m 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)
xorm 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);
These bits are used as an offset to a 64-bit table, which indicates whether to
copy a given frame or not. This table is stored in the two HASH registers, a bit
value of 1 indicating a frame should be matched, a bit value of 0 that it should
not.
HASH1 contains the 32 LSBs of the hash table with entries 0 through 31
mapped to the corresponding register bits, 0 through 31. HASH2 contains the
32 MSBs of the hash table with hash table entries 32 through 63 mapped to
register bits 0 through 31.