US Patent 7490118 Expanding instruction set using alternate error byte

Expanding the capacity of a fixed digital field using a unique number calculated from the digital field, such as an error code. Expansion is possible by calculating a new error code using a different algorithm. A recipient, upon not detecting the error code from the original algorithm, checks for the new error code before indicating an error. The presence of the new error code acts like an extra bit to give an entirely new set of numbers for the digital field, thus doubling the command set. In another aspect of the invention, fill bits between transmission packets are used to indicate further data, and are included in calculating the new error code.