Chapter 7: Using The Physical Side Interface; Implementing External Gmii; Gmii Transmitter Logic - Xilinx LogiCORE IP MAC v8.5 User Manual

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Using the Physical Side Interface
This chapter provides general guidelines for creating designs using the Physical Side
Interface of the GEMAC core. The physical side interface implements GMII-style signaling
and is typically attached to a physical layer device (PHY), either off-chip or internally
integrated. See
internal interface in conjunction with the Ethernet 1000BASE-X PCS/PMA or SGMII core,
see
The remainder of this chapter describes how to use the core with an external GMII or
RGMII. See also

Implementing External GMII

The HDL example design that is delivered with the core will implement an external GMII
when GMII is selected from the CORE Generator™ GUI (see
Core"). For more information about the example design, see the 1-Gigabit Ethernet MAC
Getting Started Guide.

GMII Transmitter Logic

Figure 7-1
external GMII in a Spartan®-3 device. The signal names and logic shown in this figure
exactly match those delivered with the example design when the GMII is selected. If other
families are chosen, equivalent primitives and logic specific to that family is used in the
example design.
Figure 7-1
driving them to the device pads. The logic required to forward the transmitter clock is also
shown. This logic uses an IOB output Double-Data-Rate (DDR) register so that the clock
signal produced incurs exactly the same delay as the data and control signals. This clock
signal, gmii_tx_clk, is inverted with respect to gtx_clk so that the rising edge of
gmii_tx_clk will occur in the centre of the data valid window, therefore maximizing
setup and hold times across the interface.
1-Gigabit Ethernet MAC v8.5 User Guide
UG144 April 24, 2009
-- DISCONTINUED PRODUCT --
"Physical Side Interface" in Chapter
Chapter 11, "Interfacing to Other Cores."
Chapter 9, "Constraining the Core"
illustrates how to use the physical transmitter interface of the core to create an
shows that the output transmitter signals are registered in device IOBs before
www.xilinx.com
Chapter 7
2. For information about using an
for a listing of required constraints.
Chapter 3, "Generating the
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