1. An interface between a physical layer local area network and a host central processing unit comprising: at least one receive channel, each receive channel including a receive multiplexer having two inputs, each input connected to a corresponding physical layer and an output, a receive interface unit having an input connected to said receive multiplexer output and an output, said receive interface unit converting received data in a first data size into data words of a second larger size, and a receive data and status unit having an input connected to said receive interface unit output and an output, said receive data and status unit including a control register and performing data manipulation on input data to generate output data, said data manipulation corresponding to data stored in said control register; at least one transmit channel, each transmit channel including a transmit data and flags unit having an input and an output, said transmit data and flags unit performing data manipulation upon input data to generate output data, a transmit interface unit having an input connected to said transmit data and flags unit output and an output connected to each physical layer, said transmit interface unit converting received data in a third data size into data words of a fourth smaller size; and a programmable real-time unit having inputs connected to said output of said receive data and status unit of a corresponding receive channel, outputs connected to said inputs of said transmit data and flags unit of a corresponding transmit channel, said programmable real-time unit bidirectionally coupled to the host central processing unit, said programmable real-time unit operable under program control to perform data processing on received data and supply data to said at least one transmit channel, said programmable real-time unit operable under program control to specify data stored in said control register.