Xilinx UG144 manual Client Side Interface, Transmitter Interface

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Chapter 2: Core Architecture

All ports of the core are internal connections in FPGA fabric. An HDL example design is delivered with the core that will add IBUFs, OBUFs, and IOB flip-flops to the external signals of the Gigabit Media Independent Interface (GMII) or Reduced Gigabit Media Independent Interface (RGMII).

All clock management logic is placed in this example design, which allows for more flexibility in implementation (for example, in designs using multiple cores). This example design is provided in both VHDL and Verilog. For more information about example designs, see the 1-Gigabit Ethernet MAC Getting Started Guide.

Client Side Interface

Transmitter Interface

Table 2-1describes the client-side transmitter signals of the GEMAC core. These signals are used to transmit data from the client logic into the core. See “Transmitting Outbound Frames,” on page 47.

The Transmitter Interface is designed to be connected to internal device logic only. Attempting to add external ports to this interface will result in a breakdown of the handshaking protocol used by this interface.

Table 2-1:Transmitter Client Interface Signal Pins

Signal	Direction	Clock	Description
		Domain
gtx_clk	Input	n/a	Clock signal provided to the core at
			125 MHz. Tolerance must be
			within IEEE 802.3-2005
			specification. This clock signal is
			used by all of the transmitter logic.
tx_data[7:0]	Input	gtx_clk	Frame data to be transmitted is
			supplied on this port.
tx_data_valid	Input	gtx_clk	Control signal for tx_data port.
tx_ifg_delay[7:0]	Input	gtx_clk	Control signal for configurable
			Inter Frame Gap adjustment.
tx_ack	Output	gtx_clk	Handshaking signal asserted when
			the current data on tx_data has
			been accepted.
tx_underrun	Input	gtx_clk	Asserted by client to force GEMAC
			core to corrupt the current frame.
tx_statistics_vector[31:0]	Output	gtx_clk	Provides statistical information
			about the last frame transmitted.
tx_statistics_valid	Output	gtx_clk	Asserted at end of frame
			transmission, indicating that the
			tx_statistics_vector is valid.

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		UG144 April 24, 2009