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5.0 Initial Values

Equations at (M-3) and (M-4) do not impose any implementation constraints on initial values when encoding or decoding starts. To confirm this it is assumed that hardware power-up (or initial data presentation) may cause encoding to commence with either channel. It is further assumed that no provisions for specific initial values in encoder and decoder state memories have been made. If coding starts with I (see equation M-3a), the first code symbol will be computed:

As can be seen, the initial values do establish the absolute sense of code symbols for the duration of transmission. But, on both ends of the process, two of three terms in every equation are affected consistently by the initial value, which by symmetry has no effect on the outcome of exclusive-or operations. Obviously, identical results occur if the encoder starts with Q. Independent of starting channel and initial value then, the first and all subsequent adjacent code symbol pairs contain valid state change information.