FOREIGN PATENT DOCUMENTS
0 196 677 A2 10/1986 European Pat. Off D03D 51/00
0 562 333 A2 9/1993 European Pat. Off G05B 19/417
0 622 712 A2 11/1994 European Pat. Off G05B 19/05
2 283 836 5/1995 United Kingdom G06F 19/00
2 283 887 5/1995 United Kingdom H04L 12/403
Primary Examiner—Reba I. Elmore
Assistant Examiner—Steven R. Garland
Attorney, Agent, or Firm—-Wolf, Greenfield & Sacks, PC.
A process control system includes a high speed serial backbone communications network, interconnecting a plurality of microprocessor based nodes that each act as the master to a high speed serial branch network comprising device controllers, such as air flow valve controllers and transducers. The primary network may operate in a time division multiplex mode whereby a node acting as a synchronizing station periodically issues a synchronizing signal that commands each node to execute a branch network control sequence, during which each node gathers and operates upon data it collects from the device controllers within its branch network, and issues commands based thereon to the branch network. An ensuing communications sequence also triggered by the synchronizing signal enables each node on the primary network to transmit a command or a response to any other node and, through such other node, to any device controller in any branch network of the system. Serial ports on each node permit user access from any node on the primary network to any other point on the system for purposes of monitoring and control. Serial ports on each device controller permit user access to local device parameters.
30 Claims, 4 Drawing Sheets