PLC chapter 3

  1. Term that refers to the CPU's act of processing the application program
    program scan
  2. A CPU feature allowing portions of program code to be executed precisely at regular intervals
    times interrupt processing
  3. These are errr or fault conditions that are detected while the CPU is processing the control program
    run-time faults
  4. a measure of how long it takes t react to an external input signal and then control an output signal
    response time
  5. CPU state that, when selected, causes program execution and I/O update on a cyclical basis
    RUN mode
  6. a special area of memory written to by the control program to control the on/off state of discrete outputs
    output image table
  7. an important calculation that determines the current consumption of a selected group of I/O modules
    power supply loading
  8. a CPU feature allowing an external input signal, when generated, to cause the CPU to stop its normal processing to process a special subroutine or portion of code
    hardware interrupt processing
  9. this nominal value expresses, in ms, the typical time required to processĀ  (1024) wrds of programmed instruction
    scan rate
  10. CPU state, when selected, causes cyclic program execution and I/O image update as in the normal RUN mode, however the real world outputs are not activated
    TEST mode
  11. a CPU feature allowing inputs to be read or outputs to be controlled whenever the appropriate instruction is encountered, instead of waiting to the normal update at the end of the program scan
    immediate I/O update
  12. CPU state that, allows the user to selectively override or alter the real world status f inputs and outputs
    I/O FORCE mode
  13. name given to the duration for which it takes the processor to perform one complete execution of the program and I/O update
    cycle time
  14. a CPU diagnostic test that monitors program scan to ensure that the normal scan time is not exceeced and is within specified limits
    watch dog timer
  15. name given to the housing that contains the central processing unit
    CPU rack
  16. solution intended for applications where downtime or process interruption must be avoided at all costs
    fault-tolerant PLC
  17. PLC design solution that allows all controlled elements to be brought to a predictable and predetermined safe-state in the case of failures internal or external to the PLC
    fail-safe PLC
  18. a special memory area reserved for storing the status of the connected discrete inputs
    input image table
  19. the process of reading the connected inputs and controlling the connected outputs
    I/O scan
  20. CPU state that, when selectred, causes program execution to be halted and outputs to e disabled
    STOP mode
  21. permanently stored program, considered part of the PLC-it determines the unique capabilities of the PLC as well as how and when certain system operations are performed
    operating system
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PLC chapter 3
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