Data handling module for programmable controller

In a programmable controller having a memory which stores a control program and a processor which sequentially and continuously reads out instructions that comprise the control program and executes them to control a machine, the combination comprising:

• an active data file storage which is coupled to said processor and which stores a data file that is operated upon by said processor in response to control program instructions which it executes to control said machine;
• a data file storage which stores a plurality of data files, each of which is suitable for storage in said active data file storage and each of which includes data to be operated upon by said processor to control said machine;
• a control status register, coupled to said processor and including a first storage location which may be set to a selected state by said processor in response to the execution of a control program instruction to indicate that the transfer of a particular data file from said data file storage to said active data file storage is to occur, file identification storage locations which may be set to a selected state by said processor to identify the particular data file to be transferred, and a second storage location which may be examined by said processor in response to the execution of another control program instruction to indicate whether or not said transfer has been completed;
• and
• a data handling module coupled to said control status register, said active data file storage and said data file storage, said data handling module including:
• (a) examining means, coupled to said control status register, for periodically examining said first storage location therein and indicating when a transfer is to occur;
• (b) selecting means, coupled to said control status register and being responsive to the contents of said file identification storage locations therein, for selecting the data file to be transferred;
• (c) transferring means, coupled to said selecting means, said active data file storage and said data file storage, for tranferring said particular data file from said data file storage to said active data file storage when the transfer is indicated by said examining means;
• and
• (d) means responsive to said transfer means and coupled to said control status register, for setting the stae of said second storage location therein to indicate that the transfer has been completed.