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1-Gigabit Ethernet MAC v8.5 User Guide
UG144 April 24, 2009
Chapter 2:
Core Architecture
R
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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 2-1
describes 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
Domain
Description
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.
