Digi NS9215 - Manual (Page 334)

E T H E R N E T C O M M U N I C A T I O N M O D U L E
Sample hash table code
334 Hardware Reference NS9215
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S a m p l e h a s h t a b l e c o d e
This sample C code describes how to calculate hash table entries based on 6-byte
Ethernet destination addresses and a hash table consisting of two 32-bit registers
(HT1 and HT2). HT1 contains locations 31:0 of the hash table; HT2 contains
locations 63:32 of the hash table.
The pointer to the hash table is bits [28:23] of the Ethernet destination address
CRC. The polynomial is the same as that used for the Ethernet FCS:
G(x) = x^32+x^26+x^23+x^22+x^16+x^12+x^11+x^10+x^8+x^7+x^5+x^4+x^2+x+1
static ETH_ADDRESS mca_address[MAX_MCA]; /*list of MCA addresses*/
static INT16 mca_count; /*# of MCA addresses*/
/ *
*
* Function: void eth_load_mca_table (void)
*
* Description:
*
* This routine loads the MCA table. It generates a hash table for
* the MCA addresses currently registered and then loads this table
* into the registers HT1 and HT2.
*
* Parameters:
*
* none
*
* Return Values:
*
* none
*
*/
static void eth_load_mca_table (void)
{
WORD32 has_table[2];
// create hash table for MAC address
eth_make_hash_table (hash_table);