Cyclone V Device Handbook: Volume 2: Transceivers

ID 683586
Date 10/24/2018
Document Table of Contents

4.2. Gigabit Ethernet

The IEEE 802.3 specification defines the 1000BASE-X PHY as an intermediate, or transition layer that interfaces various physical media with the MAC in a gigabit ethernet (GbE) system, shielding the MAC layer from the specific nature of the underlying medium. The 1000BASE-X PHY is divided into the PCS, PMA, and PMD sublayers.

The PCS sublayer interfaces with the MAC through the gigabit media independent interface (GMII). The 1000BASE-X PHY defines a physical interface data rate of 1 Gbps and 2.5 Gbps.

Figure 76. 1000BASE-X PHY in a GbE OSI Reference Model

The transceivers, when configured in GbE functional mode, have built-in circuitry to support the following PCS and PMA functions, as defined in the IEEE 802.3 specification:

  • 8B/10B encoding and decoding
  • Synchronization
  • Clock recovery from the encoded data forwarded by the receiver PMD
  • Serialization and deserialization
Note: If you enabled the autonegotiation state machine in the FPGA core with the rate match FIFO, refer to the "Rate Match FIFO" section in the "Gigabit Ethernet Transceiver Datapath" section.
Note: The transceivers do not have built-in support for other PCS functions, such as the autonegotiation state machine, collision-detect, and carrier-sense functions. If you require these functions, implement them in the FPGA fabric or in external circuits.
Figure 77. Transceiver Blocks in a GbE Configuration