478 terms ch 04

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478 terms ch 04
2013-02-19 22:03:43

478 terminology
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  1. a character, placed at the end
    of a data block, that corresponds to the characteristics of block.
    Block check character (BCC)
  2. a transmission verification algorithm that adds
    the binary values of all the characters in a data block and places the sum in
    the block check character position.
    Check sum
  3. a transformer that maintains
    a steady output voltage (secondary) regardless of input voltage (primary)
    Constant voltage transformer
  4. an error detection method
    in which the words in the data block are exclusive-ORed with the checksum word
    and then rotated to the left.
    Cyclic exclusive-OR checksum (CX-ORC)
  5. an error detection method in
    which all the bits in a block are divided by a predetermined binary number. The
    remainder becomes the block check character.
    Cyclic redundancy check (CRC)
  6. the detection and isolation of an error or
  7. an error-detecting code that combines parity
    and data bits to generate a byte containing a value that identifies the
    erroneous bit.
    Hamming code
  8. the process of revising the bits in a
    PLC’s I/O tables based on the latest results from reading the inputs and processing
    the outputs according to the control program.
    I/O update scan
  9. a transformer that protects its
    connected devices from surrounding electromagnetic interference.
    Isolation transformer
  10. an error-checking
    technique based on accumulated exclusive-OR of transmitted characters.
    Longitudinal redundancy check (LRC)
  11. a digital, electronic logic package capable
    of performing the program execution, control, and data-processing functions of
    a central processing unit. The contains an arithmetic logic unit, temporary
    storage registers, instruction decoder circuitry, a program counter, and bus
    interface circuitry.
  12. a portable device used for programming,
    changing, and monitoring a PLC’s control logic.
  13. concurrent execution of two or more tasks
    residing in memory.
  14. the even or odd characteristic of the number of 1s
    in a byte or word of memory.
  15. a bit added to a memory word as a means of
    error detection.
    Parity bit
  16. the time required by the processor to
    evaluate and execute the control logic.
    Program scan
  17. the time required to complete the scan or two
    activate and output that is controlled by programmed logic.
    Scan time
  18. an error detecting method
    in which a parity bit is added to each character in a message so that the
    number of bits in each character is either at or even.
    Vertical redundancy check (VRC)