Programmable controller with self testing I/O structure
AssigneeAllen-Bradley Company, Inc.
InventorNeil W. Knutsen
Life of this patent
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Abstract
A programmable controller includes a processor unit which connects to one or more I/O units that connect to sensing devices and operating devices on equipment being controlled. When placed in the RUN mode, the processor determines the number of I/O units required to execute the user control program, and during each subsequent I/O scan, the number of connected and operating I/O units is checked to insure proper operation.
Claims4
In a programmable controller having a processor unit which may be connected to one or more I/O expansion units, the combination comprising:
- storage means in said processor unit for storing a user control program which includes instructions that direct the examination of input devices connected to I/O expansion units and instructions that direct the operation of output devices connected to I/O expansion units;
- examination means coupled to the storage means for examining the user control program instructions and determining a highest number in a number range of the I/O expansion untis which are required to execute the user control program;
- scanner means responsive to signals from the I/O expansion units for determining a number range of I/O expansion units which are connected to the processor unit;
- comparison means coupled to the examination means and the scanner means for comparing a highest number in the number range of the I/O expansion units determined by the scanner means with the highest number in the number range of I/O expansion units determined by the examination means;
- and
- means responsive to said comparison means for preventing execution of the user control program when the highest number in the number range of the I/O expansion units determined by the scanner means does not match the highest number in the number range of I/O expansion units determined by the examination means.
In a programmable controller having a processor unit which may be connected to one or more I/O expansion units, the combination comprising:
- storage means in said processor unit for storing a user control program which includes instructions that direct the examination of input devices connected to I/O expansion units and instructions that direct the operation of output devices connected to I/O expansion units;
- examination means coupled to the storage means for examining the user control program instructions and determining addresses of the I/O expansion units which are required to execute the user control program;
- scanner means responsive to signals from the I/O expansion units for determining addresses of I/O expansion units which are connected to the processor unit;
- and
- comparison means coupled to the examination means and the scanner means for comparing the addresses of the I/O expansion units determined by the examination means with the addresses of I/O expansion units determined by the scanner means;
- and
- means responsive to said comparison means for preventing execution of the user control program when the address of the I/O expansion unit determined by the examination means is not one of the addresses of the I/O expansion units determined by the scanner means.
Dependencies are inferred from the claim text.