Maxim-integrated 78Q8430 Software Driver Manual do Utilizador descarregar pdf (Página 20)

78Q8430 Software Driver Development Guidelines UG_8430_004

STEP 2: Write address and mask byte [1] through byte [4] to the CAM.

For each byte, write the CAM rule indicated by

Table 4 based on the filter number and byte number

as follows:

Reg. Field Value to write

byte [1]: byte [2]: byte [3]: byte [4]: CAR ADDR

0x64+N 0x60+N 0x4C+N 0x48+N

Data Match Value of MAC address byte [1] … byte [4]

Data Mask Value of mask byte [1] . . . byte [4]

Previous Hit Match Value of the CAM rule used by the previous byte

RMR

Previous Hit Mask 0x7F

Byte Offset Retain default: 0x00

Interrupt Retain default: 0

Control Logic Action Retain default: NOP

RCR

Match Control Retain default: MD

For example, the Previous Hit fields for filter #1 would be 0x7D, 0x65, 0x61 and 0x4D, for byte [1]

through byte [4] respectively.

EXCEPTION: multicast filter #3, byte [4] should have the Action field set to TAX.

STEP 3: Write address and mask byte [5] to the CAM.

Write CAM rule 0x3C+N as follows:

Reg. Field Value to write

CAR ADDR 0x3C+N

Data Match Value of MAC address byte [5]

Data Mask Value of mask byte [5]

Previous Hit Match Set to the CAM rule that was used for byte [4] (0x48+N).

RMR

Previous Hit Mask 0x7F

Byte Offset Retain default: 0x00

Interrupt Retain default: 0

Control Logic Action Set to TAX

RCR

Match Control Retain default: MD

EXCEPTION: multicast filter #3, byte [5] should have the Action field set to SETBC.

STEP 4: Enable the filter.

Enable the multicast address filter N by modifying the CAM rule for byte [0]:

• Set the CAR ADDR field to 0x7C+N.

• Set the RMR Previous Hit Mask field to 0x7F.

This step must be done last to prevent an incoming frame from matching a partial set of filter rules.

All the rules for a filter must be in place before the first rule, and therefore the filter itself, is enabled.

A multicast address filter can be simply activated and deactivated by toggling the value of the RMR

Previous Hit Mask field for the byte [0] CAM rule between 0x7F and 0x00 respectively. Multicast filter #0

should not be deactivated in this way.

It is important to deactivate the filter in STEP 1 (by setting the Previous Hit Mask field to 0x00) 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.

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