Xilinx IP Ethernet AVB Endpoint v2.4 UG492 - Manual (Page 65)

Ethernet AVB Endpoint User Guide www.xilinx.com 65
UG492 September 21, 2010
Chapter 7
Ethernet AVB Endpoint Reception
Rx Splitter
The input to the Rx splitter (see Figure 5-1 ) is connected directly to the client Receive (Rx)
interface of the connected Ethernet MAC. Received data from an AVB network can be of
three types:
•
Precise Timing Protocol (PTP) Packets . Routed to the dedicated hardware “Rx PTP
Packet Buffer” which can be accessed by the “Software Drivers.” PTP packets are
identified by searching for a specific MAC Destination Address.
• AV Traffic . Routed to the “Rx AV Traffic I/F” of the core. These packets are identified
by searching for MAC packets containing a MAC VLAN field with one of two
possible configurable VLAN priority values (see
“Rx Filtering Control Register” ).
• Legacy Traffic: . Routed to the “Rx Legacy Traffic I/F” of the core. All packet types
which are not identified as PTP or AV Traffic will be considered legacy traffic.
Rx Legacy Traffic I/F
The signals forming the Rx Legacy Traffic I/F are defined in Table 5-3 . All signals are
synchronous to the Tri-Mode Ethernet MAC receiver clock, rx_clk, which must always
be qualified by the corresponding clock enable, rx_clk_en (see
Table 5-1 ).
This interface is intentionally identical to the client receiver interface of the supported Xilinx
Tri-Mode Ethernet MAC core (there is a one-to-one correspondence between signal names
of the block-level wrapper from the Tri-Mode Ethernet MAC example design, after the
legacy_
prefix is removed). This provides backward compatibility–all existing MAC
client-side designs which use the clock enable should be able to connect to the legacy
Ethernet port unmodified.
Operation of the Rx Legacy Traffic Interface is closely connected with the frame header
match results of the
“Legacy MAC Header Filters.” If the filters are enabled and do not
obtain a match, the frame data does not appear on this interface
(legacy_rx_data_valid and legacy_rx_frame_good/legacy_rx_frame_bad
are not asserted). When a match is obtained these signals are asserted as described in the
following sections.