1. A system for providing bidirectional data transfer between a host processor and a remote processor, wherein said host processor is configured to process words of a first length and wherein said remote processor is configured to process words of a second length, said system including a coupler for interfacing said processors, said coupler comprising: A. means for detecting any one of a plurality of data transfer commands from said host processor, said data transfer commands including read and write data transfer commands; B. an input register coupled for receiving data from said host processor; C. an output register coupled for receiving data from said remote processor; D. first means for transferring data from said input register to said remote processor; E. second means for transferring data from said output register to said host processor; F. means for enabling said first and second means for transferring for the transfer of data from either said input or output registers to respectively said remote and host processors in response to either said write or read commands respectively; G. status word register means comprising a plurality of bit locations, some of said locations for indicating whether a read or write data transfer command has been detected, said register means further including 1. an input counter, and 2. an output counter; H. first means for changing the value of said input counter in response to a transfer of a subportion of a said word of said first length from said host processor to said input register; I. second means for changing the value of said output counter in response to a transfer of a subportion of a said word of said second length from said output register to said host processor; J. conversion means responsive to said input and output counter, including: 1. first means for providing a conversion of a said word of said first length to a said word of said second length, and 2. second means for providing a conversion of a said word of said second length to a said word of said first length; and