Differential Signaling

Differential Signalinghttp://download.intel.com/education/highered/signal/ELCT865/Class2_10_11_12_Differential_Signaling.ppt

Current Mode Logic
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• No real spec yet but can infer operation from spec’s like PCI Express™ , Infiniband™, USB, SATA, etc.

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8b/10b: Overview

• The 10 bits are referred to as a “symbol” or a “code-group:”
• The original 8 bits are broken into a 3 bit block and a 5 bit block (each of these are called sub-blocks)
  
  • F1 -> 111 10001
• The 3 bit sub-block (labeled HGF) is encoded into 4 new bits (labeled fghj) & the 5 bit sub-block (EDCBA) is encoded into 6 new bits (abcdei)
  
  • HGFEDCBA notation commonly represents the un-encoded bits, and abcdeifghj represents the encoded bits; note that the relative order and position of the sub-blocks is switched upon encoding
    
    • HGF EDCBA -> abcdei fghj
  • Hence, an extra bit, j , is added to the newly encoded 3 bit block and an extra bit, i , to the encoded 45 bit block creating a 4 and 56 bit sub-blocks