Bus quantization effects with adapters – Altera 40-Gbps Ethernet MAC and PHY MegaCore Function User Manual
Page 57
Table 3-3: Signals of the TX Client Interface Without Adapters
In the table, <w> = 2 for the 40GbE IP core and <w> = 5 for the 100GbE IP core.
Signal Name
Direction
Description
din[<w>*64-1:0]
Input
Data bytes to send in big-Endian mode.
din_start[<w>-
1:0]
Input
Start of packet (SOP) location in the TX data bus. Only the most
significant byte of each 64-bit word may be a start of packet. Bit 63 or
127 are possible for the 40GbE and bits 319, 255, 191, 127, or 63 are
possible for 100 GbE.
din_end_pos[<w>
*8-1:0]
Input
End of packet. Any byte may be the last byte in a packet.
din_ack
Output
Indicates that input data was accepted by the IP core.
clk_txmac
Input
TX MAC clock. The minimum clock frequency is 315 MHz for the
circuit to function correctly. The
clk_txmac
and
clk_rxmac
which
clocks the RX datapath are not related and their rates do not have to
match.
The IP core reads the bytes in big endian order. A packet may start in the most significant byte of any
word. A packet may end on any byte.
To avoid sending packets before the IP core completes the reset sequence, you should ensure that the
application does not send packets on the TX client interface until after the
lanes_deskewed
signal is
asserted.
Related Information
•
40GbE IP Core Without Adapters
Illustrates the 40GbE IP core TX client interface without adapters.
•
100GbE IP Core Without Adapters
on page 3-14
Illustrates the 100GbE IP core TX client interface without adapters.
Bus Quantization Effects With Adapters
The TX custom streaming interface allows a packet to start at any of two or five positions to maximize
utilization of the link bandwidth. The TX Avalon-ST interface only allows start of packet (SOP) to be
placed at the most significant position. If the SOP were restricted to the most significant position in the
client logic data bus in the custom streaming interface, bus bandwidth would be reduced.
3-10
Bus Quantization Effects With Adapters
UG-01088
2014.12.15
Altera Corporation
Functional Description