Protocol for determining physical order of active stations on a token

Abstract

A reconfigurable serial loop or ring communication system is provided with a method and apparatus which enables stations on the loop to ascertain the address of its nearest active upstream neighbor (NAUN). A Ring Poll Frame is generated and broadcast from an originating station. The Ring Poll Frame includes a Ring Poll command, a From Address and a reset Address Recognized (AR) control bit. The first active downstream station recognizes the command with the control bit in the reset state, copies the contents of the ring poll frame and sets the bit. The set bit inhibits subsequent downstream stations from copying the frame. The first active station then generates a substantially similar formatted ring poll frame and passes it downstream. The process is continued by downstream active stations until the originating station receives a ring poll frame having a reset control bit. The reset control bit is an indication that all stations on the loop know the address of its NAUN. A ring management station may use the ring poll process to acquire information relative to the location of active stations on the ring.