Maxim Integrated 78Q8430 Software Driver - Manual (Page 16)

78Q8430 Software Driver Development Guidelines UG_8430_004
4 Packet Classification
The 78Q8430 packet classification engine consists of a content addressable memory (CAM) linked to
control logic (WCS) which provides extensive packet classification features. Refer to Packet
Classification in the 78Q8430 Data Sheet for more details on the packet classification features and
hardware support.
This section includes a summary of the CAM configuration and describes the procedures to implement
the following packet classification features:
• Address
Recognition
o Wildcard address filters
o Promiscuous mode
o Unicast address filters
o Multicast address filters
o Negative address filters
• OnNow packet recognition
• Magic Packet recognition
• Classification
Interrupts
4.1 CAM Configuration
The CAM rules are accessed indirectly one at a time via the CAM Address Register (CAR). The contents
of the rule whose number is indicated by the CAR are available for read and write via the Rule Match
Register (RMR) and the Rule Control Register (RCR). The RMR contains a template that the CAM
reference word must match in order to trigger the rule, and the RCR contains the control word passed to
the control logic when the rule is triggered.
The “Configuring the CAM” section in the 78Q8430 Data Sheet provides a complete description of the
CAM registers.
4.2 Address Recognition (ARC)
The 78Q8430 CAM is loaded with a set of default rules on reset. Some of these rules are intended as a
template to provide ARC functionality. They support four multicast and eight unicast address filters. The
last unicast ARC rule is configured by default as a promiscuous mode rule such that the ARC is in
promiscuous mode right out of reset.
Appendix A summarizes the default CAM rules.
4.2.1 Wildcard Address Filters
Use the Data Mask field in the RMR register to implement wildcard address filters. Each bit in the Data
Mask field masks the corresponding bit in the Data Match field. A mask bit is set to require that the
corresponding data bit match a specified condition or is cleared to indicate that the data bit is ignored
(wildcard bit).
Any unicast or multicast filter can be implemented with wildcards. For example, the promiscuous mode
filter (Section
4.2.3 ) has all address bits masked as wildcard bits so that any address will match. Wildcard
addresses can also be specified for the Magic Packet filter.
Table 2 illustrates how to configure the Data Mask and Data Match values for a wildcard address of
00:0010:4x:xx:xx. (x indicates a wildcard field)
16 Rev. 1.0