78Q8430 Data Sheet
DS_8430_001
STEP 4. Enable the filter. The unicast address filter is enabled by setting the Previous Hit Mask field of
the CAM rule for byte [0] to 0x7F. This step must be done last to prevent an ingressing frame
from matching a partial set of filter rules. All the rules for a filter must be in place before
enabling the filter.
An address filter can be simply activated/deactivated by toggling the value of the Previous Hit Mask field
for the byte [0] CAM rule between 0x7F and 0x00 respectively. The promiscuous mode filter, filter #0,
should not be deactivated in this way.
It is important that STEP 1 deactivates the filter so that no frames are filtered using a partial filter
setting before all relevant rules are written. Step 4 reactivates the filter once the new settings are in
place.
6.7.1.4 Multicast Address Filters
The default CAM rule set supports four multicast address filters. The first, multicast filter #0, serves the same
purpose as the promiscuous mode filter except it applies only to multicast addresses. The last, multicast filter
#3, is the broadcast filter and is reserved for that purpose. The second, multicast filter #1, is the PAUSE filter
and is setup by default to match the PAUSE address. Multicast filter #2 is unused by default and available for
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
CAM rule assigned to it. Table 25 summarizes the association of multicast filter bytes and CAM rules.
Table 25: CAM Rules Associated with Multicast Filter Bytes
Byte [0]
0x7F
Byte [1]
0x67
Byte [2]
0x63
Byte [3]
0x4F
Byte [4]
0x4B
Byte [5]
0x3F
M/C Filter #3
M/C Filter #2
M/C Filter #1
0x7E
0x66
0x62
0x4E
0x4A
0x3E
0x7D
0x65
0x61
0x4D
0x49
0x3D
Note: Bytes are in network transmit order starting with Byte [0].
For an arbitrary multicast filter number N, the following procedure should be used to set the address and
mask values:
STEP 1. Write address and mask byte [0] to CAM rule 0x7C+N as follows.
Reg.
Field
Value to write
CAR
ADDR
0x7C+N
RMR Data Match
Data Mask
Value of MAC address byte [0]1
Value of mask byte [0]1
0x00 to disable the filter
0x00
Previous Hit Match
Previous Hit Mask
RCR Byte Offset
Retain default: 0x00
Retain default: 0
Interrupt
Control Logic Action
Match Control
SETMC
Retain default: MD
1The LSB of both address byte [0] and mask byte [0] must be set for multicast address filters. If the
LSBs are not set then the address is not multicast and belongs in the unicast filter set.
36
Rev. 1.2
TERIDIAN [ TERIDIAN SEMICONDUCTOR CORPORATION ]
