Patent Number: 6,169,929

Title: Automatic polling for user interrupts in a programmable controller using relay ladder logic

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.

Inventors: Izzo; Joseph P. (New Berlin, WI), Whitsitt; Steven L. (Waukesha, WI)

Assignee: Rockwell Technologies, LLC

International Classification: G05B 19/05 (20060101); G06F 009/06 (); G06F 015/76 (); G05B 019/00 ()

Expiration Date: 01/02/2018