The HD-6409 Manchester Encoder-Decoder (MED) is a high
speed, low power device manufactured using self-aligned
silicon gate technology. The device is intended for use in
serial data communication, and can be operated in either of
two modes. In the converter mode, the MED converts Non
return-to-Zero code (NRZ) into Manchester code and
decodes Manchester code into Nonreturn-to-Zero code. For
serial data communication, Manchester code does not have
some of the deficiencies inherent in Nonreturn-to-Zero code.
For instance, use of the MED on a serial line eliminates DC
components, provides clock recovery, and gives a relatively
high degree of noise immunity. Because the MED converts
the most commonly used code (NRZ) to Manchester code,
the advantages of using Manchester code are easily realized
in a serial data link.
In the Repeater mode, the MED accepts Manchester code
input and reconstructs it with a recovered clock. This
minimizes the effects of noise on a serial data link. A digital
phase lock loop generates the recovered clock. A maximum
data rate of 1MHz requires only 50mW of power.
Manchester code is used in magnetic tape recording and in
fiber optic communication, and generally is used where data
accuracy is imperative. Because it frames blocks of data, the
HD-6409 easily interfaces to protocol controllers.