Low overhead closed loop control system

A tool, including:

• a process chamber;
• a communication network configured to transmit messages to and from a plurality of devices coupled to the communication network, at least some of the messages including a header portion and a data portion, the header portion of a particular message indicating a sender of the particular message and at least one intended recipient of the particular message;
• a pressure sensor configured to measure a pressure within the process chamber, the pressure sensor being coupled to the communication network;
• a tool controller coupled to the communication network;
• and
• a pressure controller coupled to the communication network, the pressure controller configured to control the pressure within the process chamber in response to measurements of the pressure within the process chamber provided by the pressure sensor and in response to a set point provided by the tool controller, the set point representing a desired pressure within the process chamber, the pressure controller including a local message processor and a local control processor, the local message processor passing at least part of a data portion of a first set of messages and a second set of messages to the local control processor, each message in the first set of messages having a header indicating the pressure controller as at least one of the intended recipients, at least some of the messages in the second set including headers that do not specify the pressure controller as one of the intended recipients.