Microprocessor-based keyboard/display unit for configuring control instruments

In an industrial process control system in which process variables are measured and such measurements are used by control instruments in developing process control signals, a keyboard/display unit comprising:

• a first microprocessor,
• means for connecting said keyboard/display unit to one of a plurality of control instruments for supplying data and/or commands to said control instrument from said keyboard/display unit and for providing information from said control instrument to said keyboard/display unit,
• a keyboard having a plurality of keys through which data and/or commands may be supplied to said microprocessor for input to a control instrument to which said keyboard/display unit is connected, said data and/or commands being used by said control instrument to determine the type of process control signals that are developed,
• a display controlled by said first microprocessor, and
• a read only memory in which is stored an operating program for said first microprocessor, said operating program defining the functions associated with at least some of said keys of said keyboard,
• said keyboard/display unit being responsive to signals from the particular control instruments to which said keyboard/display unit is connected so that upon receipt at said unit of a signal from a first type of control instrument at least some of said keys of said keyboard are defined by said operating program to have first functions with respect to the input of data and/or commands to said first type of control instrument and upon receipt at said unit of a signal from a second type of control instrument said keys are defined by said operating program to have second functions with respect to the input of data and/or commands to said second type of control instrument, whereby the same keys supply different data and/or commands to different types of control instruments upon being connected thereto.