1

1.11.2.2 Differential Manchester encoding

or ¯ at start of bit cell if next bit is a 0, no transition if next bit is a 1, always ¯ or in mid cell.

Figure 1.10 Differential Manchester Encoding

There are alternative encodings, depending on the previous bit value and hence current level and which are inversions of each other (see two alternatives in figure 1.10). To ensure absolute coding, it is necessary to transmit a known bit at the start of the sequence. Manchester encoding is often used as part of block transmission (or similar) with a known start sequence which provides the known bits.

Note that tx data stream in both forms of Manchester encoding has a clock frequency which is twice that of the data bit stream. See the rules and drawback of the differential Manchester encoding.