Maxim-integrated 78Q8430 Software Driver Manual de usuario descargar pdf (Pagina 21)

UG_8430_004 78Q8430 Software Driver Development Guidelines

Rev. 1.0 21

4.2.6 Negative Address Filters

Any address filter, either multicast or unicast, can be set as either a positive or negative filter. A positive

filter is a filter that passes frames with a source MAC address that matches the filter. A negative filter is a

filter that blocks frames with a source MAC address that matches the filter. By default, all filters are

positive acting. Use the following procedure to change a filter to negative action:

STEP 1: Change the Match Control field for the CAM rule for byte [5] from MD to DROP.

• Set the CAR Address field to the address for the CAM rule byte [5].

• Change the RCR Match Control field from MD to DROP.

To change a filter back to a positive acting filter, change the same Match Control field back to MD.

4.3 OnNow Packet Recognition

Identifying an OnNow frame is based on matching a sequence of bytes, some of which may be masked

off. The CAM contains six rules (rules 0x15 down through 0x10) reserved for OnNow pattern matching

such that it can match a sequence of up to 6 bytes. The OnNow rules are set up such that they will start

matching in the IP payload section of a frame that has already passed the address filters and IP header

checks. If rule 0x15 is disabled, the CAM no longer identifies the specified OnNow pattern.

4.3.1 Enable OnNow

Use the following procedure to enable the OnNow feature:

STEP 1: Modify CAM rule 0x15 to enable the filter.

• Set the CAR Address field to 0x15.

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

4.3.2 Disable OnNow

Use the following procedure to disable the OnNow feature:

STEP 1: Disable CAM rule 0x15.

• Set the CAR Address field to 0x15.

• Set the RMR Previous Hit Mask field to 0x00.

4.3.3 Set the OnNow Pattern

Use the following procedure to set the OnNow pattern:

STEP 1: Write byte [0] and mask to the CAM.

Write CAM rule 0x15 as follows:

Reg. Field Value to write

CAR ADDR 0x15

Data Match Pattern byte [0]

Data Mask 0x00 to mask, else 0xFF

Previous Hit Match Retain default: 0x23

RMR

Previous Hit Mask 0x00

Byte Offset Retain default: 0x00

Interrupt Retain default: 0

Control Logic Action Retain default: NOP

RCR

Match Control Retain default: MD

1 2 ... 16 17 18 19 20 21 22 23 24 25 26 ... 53 54

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Maxim-integrated 78Q8430 Software Driver Manual de usuario Pagina 21

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