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The Encoding

Manchester Encoding involves a transmitter that encodes clock and data signals in a synchronous bit stream, such that each bit represents a signal transition. The following table shows how each bit setting is defined for an encoding.

Bit Setting	Transition	Encoded Waveform
1	1 to 0
0	0 to 1

Transitions in the Manchester Encoding always occur at the center of each clock cycle. The transition at the center is defined by the bit value. Transitions at the edges of data periods are possible, depending on the values of the previous and next bits. Consider the following diagram.

As the Manchester encoded signal in the diagram shows:

• The value of 1 for the first bit forces a high-to-low transition at the center of that bit.

• The value of 0 for the second bit forces a low-to-high transition at the center of that bit and, because the first bit transitioned from high-to-low, no transition occurs at the start of that bit.

• The value of 0 for the third bit forces a low-to-high transition at the center of that bit and because the second bit transitioned from low-to-high, a high-to-low transition occurs at the start of that bit.

• The value of 1 for the fourth bit forces a high-to-low transition at the center of that bit and, because the third bit transitioned from low-to-high, no transition occurs at the start of that bit.

• The value of 0 for the fifth bit forces a low-to-high transition at the center of that bit and, because the fourth bit transitioned from high-to-low, no transition occurs at the start of that bit.

Background on Manchester Encoding

The Receiver