Automatic polling for user interrupts in a programmable controller using relay ladder logic
AssigneeRockwell Technologies, LLC
InventorsJoseph P. Izzo, Steven L. Whitsitt
Life of this patent
Estimating the term…
Abstract
A programmable controller includes memory for storing a ladder logic control program having a plurality of ladder logic instruction rungs. Each rung begins with a start of rung (SOR) instruction. A processor is coupled to the memory for executing the ladder logic control program. User interrupts are disabled during execution of the rungs. During execution of the SOR instruction, a predetermined register, such as a MCR register, is read causing simultaneous enabling of user interrupts which overrides the previously disabled user interrupts to allow the processor to receive an interrupt request signal. The interrupt request signal is received before the read function of the predetermined register has completed.
Claims16
A programmable controller for controlling the outputs to a plurality of output devices relative to inputs, comprising:
- memory means for storing a ladder logic control program having a plurality of ladder logic instruction rungs, each of said rungs having a start of rung function;
- processor means coupled to the memory means for executing the ladder logic control program, the processor means coupled to an I/O module for receiving inputs and sending signals to the plurality of output devices relative to said inputs, the processor having means for disabling user interrupts during execution of said rungs;
- and
- means for reading a predetermined register while simultaneously enabling user interrupts causing an overriding of said means for disabling user interrupts to allow the processor means to receive an interrupt request signal until the time the predetermined register has completed being read.
Method for providing automatic polling for user interrupts on a programmable controller having a ladder logic control program, the ladder logic control program having a series of rungs, each of said rungs beginning with a start of rung function, the method comprising the steps of:
- disabling user interrupts during execution of said rungs of the ladder logic control program;
- and
- reading a predetermined register of the programmable controller while simultaneously and momentarily enabling a user interrupt signal processed on the controller causing an overriding of said step of disabling user interrupts to allow a processor of the programmable controller to receive an interrupt signal request before the step of reading the predetermined register has completed.
Dependencies are inferred from the claim text.