2.1.2.2 NRZ and Manchester Coding

Within this document the following wording is used:

The expression data “bit” describes the real information content that will be broadcast. This information can be coded in “symbols” (sometimes also called “chips”) that are then physically transmitted from sender to receiver. The receiver has to decode the “symbols” back into data “bits” to access the information. The “symbol rate” is, therefore, always greater than or equal to the “bit rate”.

The ATA8510/15 supports two coding modes: Manchester coding and non-return-to-zero (NRZ) coding. NRZ coding is implemented in a straightforward manner: one bit is represented by one symbol.

Manchester coding implements two symbols per data bit. There is always a transition between the two symbols of one data bit so that one data bit always consists of a ‘0’ and a ‘1’. The polarity can be either way, as shown in the following figure.

Manchester coding has many advantages, such as simple clock recovery, no DC component and error detection by code violation. Drawbacks are the coding/decoding effort and the increased symbol rate, which is twice the data rate.