Background collection of diagnostic data from field instrumentation devices

A process control system comprising:

• a process controller located in a plant and executing one or more process control routines to control a process, the process controller configured to:
• (a) receive measurements of process parameters for the process, and (b) generate control signals for controlling the process based on the process control routines and the measurements of process parameters;
• an input/output device communicatively coupled to the process controller;
• a plurality of field devices communicatively coupled to the input/output device via a bus and, via the input/output device, to the process controller, at least one of the plurality of field devices generating a value of a dynamic device diagnostic parameter, the at least one of the plurality of field devices configured to:
• (a) measure the measured process parameters, or (b) actuate in response to receiving the control signals;
• wherein the input/output device is configured to:
• (a) route the measured process parameters received from the at least one of the plurality of field devices to the process controller via a backplane to which the process controller is connected, and (b) route the control signals received from the process controller via the backplane to the field device;
• a device tag associated with the at least one field device;
• and
• one or more memory devices storing:
• (a) data for configuring the input/output device to perform prioritized operations including a low priority retrieval of the value of the dynamic device diagnostic parameter, such that real-time process control communications performed by the input/output device receive priority over the low priority retrieval;
• (b) a first routine operable to cause the input/output device to:
• (i) retrieve the value of the dynamic device diagnostic parameter generated by the at least one field device, and
• (ii) cache the value of the dynamic device diagnostic parameter retrieved from the at least one field device before the value of the dynamic device diagnostic parameter is used to perform a process control function;
• and
• (c) a second routine operable to read the stored value of the dynamic device diagnostic parameter from the cache and perform the process control function using the value of the dynamic device diagnostic parameter.