Patent ID: 7882289

Claim:
A slave apparatus in a data transmission system in which a plurality of slave apparatuses which are lower-ranked apparatuses are connected to a master apparatus which is the highest-ranked apparatus in a cascade configuration, comprising: an identification number retention section to retain the same identification number as other slave apparatuses; a receiver to receive data to which an apparatus number specifying one of said plural slave apparatuses is added from said master apparatus or other slave apparatus connected to the higher-rank side of said slave apparatus; a judgment section to judge that the data is destined for said slave apparatus itself when the apparatus number added to the data received by said receiver coincides with the identification number, whereas to judge that the data is destined for another slave apparatus when the apparatus number does not coincide with the identification number; a transmitter, when said judgment section judges that the data is destined for another slave apparatus, subtracts or adds a predetermined value from or to the apparatus number to change the apparatus number, adds the changed apparatus number to the data and transmits the data to another slave apparatus connected to the lower-rank side of said slave apparatus; a response transmitter to add the identification number as an apparatus number to response data to said master apparatus, and to transmit the response data to said master apparatus or another slave apparatus connected to the higher-rank side of said slave apparatus; and a response receiver to receive response data transmitted from said response transmitter of other slave apparatus connected to the lower-rank side of said slave apparatus; when said response receiver receives the response data from another slave apparatus connected to the lower-rank side of said slave apparatus, said response transmitter to add or subtract the predetermined value to or from the apparatus number added to the response data to change the apparatus number to reverse the subtracting or adding performed by said transmitter of said slave apparatus, to add the changed apparatus number to the response data, and to transmit the response data to said master apparatus or another slave apparatus connected to the higher-rank side of said slave apparatus.