78Q8430 Data Sheet
DS_8430_001
6.7.1 Address Filtering
The 78Q8430 CAM is loaded upon reset with a set of default rules for users who only want to use the
address filter feature (see Section 6.7.4). The following rules are intended as a template to provide
address-filtering functionality. They support four multicast and eight unicast address filters. The last
unicast address filter rule is configured by default as a promiscuous mode rule such that the address-filter
is in promiscuous mode right out of reset.
6.7.1.1 Promiscuous Mode Off
In promiscuous mode, all addresses are passed on to the host driver. This means that, as long as
promiscuous mode is enabled, none of the other address filters are effective. Promiscuous mode must
therefore be disabled before any address filtering can happen. The following procedure should be used
to deactivate promiscuous mode:
STEP 1. Change the Match Control field of rule 0x30 from MD to DROP. This will cause any frame with
an address that does not match any other address filter to be dropped.
6.7.1.2 Promiscuous Mode On
The promiscuous mode filter is a filter with all address bits masked as wildcard bits such that any address
will match. Turning promiscuous mode on and off is the same as changing the promiscuous mode filter
from a positive filter to a negative filter (see Section 6.7.1.5). The following procedure should be used to
activate promiscuous mode:
STEP 1. Change the Match Control field of rule 0x30 from DROP to MD. This will cause all frames to
pass the address filters.
6.7.1.3 Unicast Address Filters
The default CAM rule set supports eight unicast address filters. The first, unicast filter #0, is the
promiscuous mode filter and is reserved for that purpose. The remaining seven are general use. Each
filter has two components, the 48-bit address that it matches and a mask that defines which bits of the
address are relevant and which bits are wildcards. Each byte of each address filter has a rule assigned
to it. The following table summarizes the association of unicast filter bytes and CAM rules.
Table 24: CAM Rules Associated with Unicast Filter Bytes
Byte [0]
0x77
0x76
0x75
0x74
0x73
0x72
0x71
Byte [1]
0x6F
0x6E
0x6D
0x6C
0x6B
0x6A
0x69
Byte [2]
0x5F
0x5E
0x5D
0x5C
0x5B
0x5A
0x59
Byte [3]
0x57
0x56
0x55
0x54
0x53
0x52
0x51
Byte [4]
0x47
0x46
0x45
0x44
0x43
0x42
0x41
Byte [5]
0x37
0x36
0x35
0x34
0x33
0x32
0x31
U/C Filter #7
U/C Filter #6
U/C Filter #5
U/C Filter #4
U/C Filter #3
U/C Filter #2
U/C Filter #1
Note: Bytes are in network transmit order starting with Byte [0].
34
Rev. 1.2
TERIDIAN [ TERIDIAN SEMICONDUCTOR CORPORATION ]
