a method for communicating on a scsi bus permits out - of - band addressing and communication for normally non - addressable devices such as scsi expanders and terminators . the method remaps 18 scsi data lines for out - of - band operation and manipulates no more than those data lines . some of the data lines are remapped for purposes of out - of - band signaling and data transfers . advantageously , manipulation of only the scsi data lines prevents the possible response of a device on the scsi network that does not support the out - of - band operations . accordingly , the disclosed method is backward compatible with existing scsi networks while allowing implementation of devices having the increased functionality of out - of - band communication .