CX82100 Home Network Processor Data Sheet
the LLC sublayer along with a status code indicating reception_complete or
reception_too_long (longer than 1518 bytes).
To support this requirement, address filtering (see Section 7.8.4) is to be used. Address
filtering is very computation intensive since it is required to be performed on every
packet on the Ethernet, regardless of its intended destination. Address filtering will be
supported in the RMAC hardware for "Destination Address" only. Nevertheless, the
software will be capable to program the hardware to promiscuous mode (see page 7-22),
which would pass all packets. Also, the software will be able to program the hardware to
pass bad packets. Therefore, the software will have flexibility to handle address filtering
if it so chooses.
The RMAC hardware will also provide hooks to the software to support
reception_complete or reception_too_long to allow compliance with the 802.3
specification requirement. These conditions are reported in the status qword.
7.8.3
7.8.4
Support for the Reception With Contention
EMx_COL asserted indicates collision detected. RMAC is required to distinguish frame
fragments received during collisions from valid frames. It will be implemented in
hardware. Early collisions will be ignored. Late collisions, after DMAC transfer
initiation, will be reported in the RMAC status qword as bit LC (late collision).
Address Filtering
The HNP EMAC supports address filtering in hardware for full 48-bit Ethernet
destination addresses only. The process for setting up the address filters and configuring
the filtering modes are described in the next few sections.
Setup Frame
The TMAC and RMAC operate independently during normal operation except during
setup frames. Setup frames are not transmitted on the MII interface but are looped back
from the TMAC to the RMAC and are used to program the address filters. A setup frame
defines the Ethernet addresses that are used to filter all incoming frames and must be
processed before the reception process is started, except when it operates in promiscuous
filtering mode. When processing the setup frame, the receiver logic temporarily
disengages from the MII interface and the transmission process must be running. The
setup frame is processed after all preceding frames have been transmitted and the current
frame reception (if any) is completed. The setup frame size must be exactly 192 bytes
(see Table 7-4).
Perfect Address Filtering
The HNP system can store up to 16 full 48-bit Ethernet destination addresses. RMAC
compares the destination address of any incoming frame to these addresses and decides
whether to reject or accept the frame based on the filtering mode configured in the
E_NA_1 or E_NA_2 register (defined in Section 7.11.3). This filtering method is called
perfect address filtering (as opposed to the hashing-based imperfect address filtering
defined in this section) because it accepts addresses that
•
•
Do not match if in inverse filtering mode (defined in this section).
Match if not in inverse filtering mode.
Table 7-4 shows the perfect address filtering Setup Frame format in the host memory.
The RMAC only keeps the column labeled "15....0" in a 48 x 16-bit hardware buffer.
7-16
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