GTS Ethernet Intel® FPGA Hard IP User Guide

ID 817676
Date 4/01/2024
Public

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4.4.1. PCS Mode TX Interface

The GTS Ethernet Intel® FPGA Hard IP TX client interface in PCS variations employs the Media Independent Interface (MII) protocol.

The client acts as a source and the TX PCS acts as a sink in the transmit direction.

Table 27.  MII TX Client Interface SignalsAll interface signals are clocked by the i_clk_tx The signal names are standard MII interface signals.
Signal Name Width Description
i_tx_mii_d[63:0] 64 bits (10GE/25GE) TX MII data. Data must be in MII encoding. i_tx_mii_d[7:0] holds the first byte the IP core transmits on the Ethernet link. i_tx_mii_d[0] holds the first bit the IP core transmits on the Ethernet link. Alignment marker counts need to be done using valid cycles. When i_tx_mii_valid is low, the alignment marker counters and input must freeze, the same as data.
i_tx_mii_c[7:0] 8 bits (10GE/25GE) TX MII control bits. Each bit corresponds to a byte of the TX MII data signal. For example, i_tx_mii_c[0] corresponds to i_tx_mii_d[7:0]. If the value of a bit is 1, the corresponding data byte is a control byte. If the value of a bit is 0, the corresponding data byte is data.
i_tx_mii_valid 1 bit

Indicates that the TX MII data signal is valid.

You must assert this signal a fixed number of clock cycles after the IP core raises ready signal, and must deassert this signal the same number of clock cycles after the IP core deasserts the ready signal. The number must be in the range of 1–6 clock cycles.

o_tx_mii_ready 1 bit Indicates that the IP is ready to receive the data. The cadence of this signal carries the line rate information in units of 66 bits.
i_tx_mii_am 1 bit Alignment marker insertion bit. Assign this signal to 0 if Firecode FEC is enabled.

The figure below shows how to send packets directly to the PCS TX interface.

Figure 35. Transmitting Data on the PCS Mode TX Interface
  • The packets are sent using MII.
    • Each byte in i_tx_mii_d has a corresponding bit in i_tx_mii_c that indicates whether the byte is a control byte or a data byte; for example, i_tx_mii_c[0] is the control bit for i_tx_mii_d[7:0].
  • i_tx_mii_valid should conform to these conditions:
    • Assert the valid signal only when the ready signal is asserted, and deassert only when the ready signal is deasserted.
    • The two signals can be spaced by a fixed latency between 1 and 6 cycles.
    • When the valid signal deasserts, i_tx_mii_d and i_tx_mii_c must be paused.
  • The byte order for the PCS mode TX interface is opposite to the byte order of the MAC Avalon® streaming interface. Bytes flow from LSB to MSB; the first byte to be transmitted from the interface is i_tx_mii_d[7:0].
  • The bit order for the PCS mode TX interface is the same as the bit order of the MAC client. The first bit to be Transmitted from the interface is i_tx_mii_d[0].
Note: The PCS TX interface is not SOP aligned. Any legal ordering of packets in MII format is accepted.
Table 28.  Sending a Start Packet Block with Preamble to the PCS TX Interface
MII Data MII Control Ethernet Packet Byte
i_tx_mii_d[7:0] 0xFB i_tx_mii_c[0] 1 Start of Packet
i_tx_mii_d[15:8] 0x55 i_tx_mii_c[1] 0 Preamble
i_tx_mii_d[23:16] 0x55 i_tx_mii_c[2] 0 Preamble
i_tx_mii_d[31:24] 0x55 i_tx_mii_c[3] 0 Preamble
i_tx_mii_d[39:32] 0x55 i_tx_mii_c[4] 0 Preamble
i_tx_mii_d[47:40] 0x55 i_tx_mii_c[5] 0 Preamble
i_tx_mii_d[55:48] 0x55 i_tx_mii_c[6] 0 Preamble
i_tx_mii_d[63:56] 0xD5 i_tx_mii_c[7] 0 SFD