Monitoring of data transfer system having serially distributed data ports

Abstract

A data transfer system having a serially distributed chain of input data ports and a serially distributed chain of output data ports is monitored to count the number of ports in each chain and to determine whether there has been a change in the configuration of the system by comparing the presently obtained counts with counts stored from previous monitoring. To monitor the system, successive data frames are serially shifted bit-by-bit from a transmitter over an output data line connecting the output data ports. Each frame contains a single unique bit in a data bit position that changes progressively from one frame to the next in relation to the position of the data ports. Upon the conclusion of each frame shift, a return data transfer circuit transfers data from the output data line to the input data line. Successive data frames are shifted over the input data line by the input data ports to the receiver synchronously with shifting the data frames over the output data line; and the received data frames are inspected by a computer to detect a frame containing a unique data bit. The computer counts the number of data frames shifted from the transmitter prior to such detection to provide an indication of the number of output data ports, and detects the position of the unique data bit in the detected frame to provide an indication of the number of input data ports.