Maxim Integrated 78Q8430 Software Driver - Manual (Page 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