TLK1221

SLLS713C – FEBRUARY 2007 – REVISED SEPTEMBER 2009....................................................................................................................................... www.ti.com

APPLICATION INFORMATION

8b/10b Transmission Code

The PCS maps GMII signals into ten-bit code groups and vice versa, using an 8b/10b block coding scheme. The

PCS uses the transmission code to improve the transmission characteristics of information to be transferred

across the link. The encoding defined by the transmission code ensures that sufficient transitions are present in

the PHY bit stream to make clock recovery possible in the receiver. Such encoding also greatly increases the

likelihood of detecting any single- or multiple-bit errors that may occur during transmission and reception of

information. The 8b/10b transmission code specified for use has a high transition density, is run length limited,

and is dc-balanced. The transition density of the 8b/10b symbols ranges from 3 to 8 transitions per symbol. The

definition of the 8b/10b transmission code is specified in IEEE 802.3 Gigabit Ethernet and ANSI X3.230-1994

(FC-PH), clause 11.

8b/10b transmission code uses letter notation describing the bits of an unencoded information octet. The bit

notation of A, B, C, D, E, F, G, H for an unencoded information octet is used in the description of the 8b/10b

transmission code-groups, where A is the LSB. Each valid code group has been given a name using the

following convention: /Dx.y/ for the 256 valid data code-groups and /Kx.y/ for the special control code-groups,

where y is the decimal value of bits EDCBA and x is the decimal value of bits HGF (noted as K<HGF.EDCBA>).

Thus, an octet value of FE representing a code-group value of K30.7 would be represented in bit notation as 111

11110.

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