Executing downloaded user programs in a programmable controller

In a programmable controller, a method of operating an I/O module for controlling machine interface outputs which, during operation, are connected to I/O devices on controlled equipment, wherein the machine interface outputs are controlled in response to signals received from a plurality of machine interface inputs which, during operation, are connected to I/O devices on controlled equipment, the method comprising:

• receiving a file of higher-level instructions within a I/O module, said file of higher-level instructions being received from a processor-based program node, and said file of higher-level instructions including an output instruction for executing an output function and for controlling a machine interface output according to the output function;
• translating said file of higher-level instructions to a data structure which, according to the output function, relates a logic state for the machine interface output to logic states sensed for signals received through the plurality of machine interface inputs;
• and
• after translating said file of higher-level instructions, executing an I/O control routine of lower-level instructions for controlling the logic state of the machine interface output in response to logic state sensed from signals from the inputs and according to the relationship established in said data structure during the translating step.

An I/O module with machine interface inputs and machine interface outputs for connection to I/O devices on controlled equipment and with means for connection to a controller processor through a communication link, the I/O module comprising:

• means on the I/O module for receiving a program downloaded from the controller processor, the program including output instructions for determining logic states of the machine interface outputs in response to logic states of the machine interface inputs on the I/O module;
• storage means on the I/O module for storing the program received from the controller processor;
• means on the I/O module coupling said means for receiving to said storage means for communicating said program to said storage means;
• means on the I/O module coupled to the storage means for executing the output instructions in the program to control the logic states of the machine interface outputs on the I/O module in response to the logic states of the machine interface inputs on the I/O module to complete a control loop through the machine interface inputs to the machine interface outputs of the I/O module.