| abstract |
A plurality of gas flow control units in cabinets are connected to distribute process gas, on demand, to a plurality of utilization locations known as "tool" locations in a semi-conductor manufacturing plant. Each gas flow control unit is connected to a single tool interface controller over a single communications cable. The status and operational characteristics of the individual units are communicated through the tool interface controller to a supervisory control computer by means of polling. Each flow control cabinet has its own data processor, and can be operated alone. Also, the supervisory computer can be used to operate each cabinet, as well as to monitor operations of the system. Gas demand and other signals are communicated from each tool locations to the control units through a single cable connected to the interface controller, thusreducing the original wiring cost. Changing the communications path to accompany a change of the tool to which a given conduit in one of the cabinets delivers its gas can be done quickly, in software, with a few keystrokes. Mechanical re-wiring is not needed. |