Ethernet Families

The Ethernet physical layer has evolved over time to utilize several media interfaces and transmission speeds, for example:

Physical Media

  • Co-axial
  • Twisted Pair
  • Fiber-Optic


  • 1 Mbps
  • 10 Mbps
  • 100 Mbps
  • 1000 Mbps
  • 10 Gbps
  • 100 Gbps

Ethernet Family Naming Scheme

Ethernet families are named according to certain medium specifications:


For example, Fast Ethernet is named:


Bit Rate

The nominal usable speed for the MAC layer.


  • 10, 100, 1000 (no suffix = megabits/second)
  • 10G (G suffix = gigabits/second)

Signaling Type

  • BASE - Baseband signaling (most common type)
  • BROAD - Broadband signaling
  • PASS - Passband signaling


PCS Encoding

Certain bit encoding schemes are employed at certain speeds to reduce the required transmission bandwidth.

  • X = 8b/10b block encoding (Gigabit ethernet) or 4b/5b (Fast ethernet)
  • R = 64b/66b for large blocks (10G ethernet)


Refers to the number of signal-carrying wires (or wire-pairs) used per link (1, 2, 4, 10).

Common Families Supported by Microchip's Ethernet Portfolio

Family Type Medium Data Rate Segment Length
10BASE-T UTP* 10 Mbps 100 m
100BASE-TX 2-Pair CAT5 UTP 100 Mbps 100 m
100BASE-FX 2 Optical Fibers 100 Mbps 100 m
1000BASE-T 4-Pair CAT5 UTP 1000 Mbps 100 m

UTP - Unshielded twisted pair

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