Programmable controller having forcibly set or reset I/O states controlled by stored flags in a flag memory

Claim 1

A programmable controller having an input/output simulation function for debugging user programs and comprising: an input/output memory means for storing a plurality of input/output data items, said input/output memory means including means for writing input/output data items into said input/output memory means during an execution of a programmed command or during an updating of input data; flag memory means for storing a plurality of flag data items, said flag memory means storing a number of flag data items which corresponds in number to a number of input/output data items stored in said input/output memory means, each said flag data item corresponding to a respective input/output data item; means for setting predetermined values of said input/output data items at selected addresses in said input/output memory means; and control means for controlling said writing means to control the writing of input/output data items into said input/output memory means, said control means operating, during the execution of a programmed command or during the updating of input data, to inhibit the writing of input/output data items in said input/output memory means where a corresponding flag data item in said flag memory has been set, said setting means, when setting a selected input/output data item in said input/output memory means also setting in said flag memory means a flag value corresponding to the selected input/output data item.