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Storing and Organizing Data

Storing and Organizing Data. Why Do I Need to Understand How Data Is Represented?. In order to install, program,maintain, and troubleshoot today’s PLCs, you must understand the different methods by which internal data is represented. Objectives.

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Storing and Organizing Data

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  1. Storing and Organizing Data

  2. Why Do I Need to Understand How Data Is Represented? • In order to install, program,maintain, and troubleshoot today’s PLCs, you must understand the different methods by which internal data is represented.

  3. Objectives • Identify the commonly used number systems used in PLCs. • Convert binary data to decimal. • Examine how data is stored in PLC data tables. • Describe how BCD field devices interface.

  4. PLC Words • One measure of a computer’s capabilities is the length of the data words on which it can operate. • Many current PLCs use 16-bit words. • Many newer PLCs use 32-bit words. • SLC 500 and PLC 5 family PLCs are 16-bit computers. • Control Logix is a 32-bit computer.

  5. Number Systems Typically Used with PLCs

  6. We Use Words to Represent Information • Our words are groups of characters grouped together to represent something. • The words we use are of different lengths. • Controller • The • Monday

  7. We Use Symbols Called Numbers to Represent Data • Everyday numbers are decimal. 12,345

  8. Computers Do Not Understand • Computers do not understand the words and numbers humans use. • Computers have their own language called binary.

  9. Binary Concept • Two-state devices are described as either discrete or digital devices. • Discrete or digital devices are simply either on or off. • Binary is based on two states, on or off.

  10. Binary Language • Binary information is also represented in groups of characters. • A group of binary digits called bits can be organized into words. • Binary bits consist of only two characters • 1 and 0

  11. Binary Words • 16 bits grouped together is called a word. • A binary word might look like: 1010 1010 1010 1010 1010

  12. Information Represented as Combinations of Bits

  13. Decimal Numbers • Ten digits • 0,1,2,3,4,5,6,7,8,9 • Base or radix • 10 • Weights • 1, 10, 100, 1000

  14. Decimal Number System

  15. The Binary Number System Has the Following Characteristics • Two digits • 0 or 1 • Base or radix • 2 • Weights • 1, 2, 4, 8, 16, 32, 64…

  16. 16-bit Binary Word Bit Weighting MSBLSB • LSB = least significant bit • MSB = most significant bit

  17. Binary Numbers Place Values

  18. Binary Number Weighting

  19. Decimal 0 through 7 Represented with Binary Bits

  20. Comparison of Decimal to Binary Numbers

  21. Parts of a 16-bit Word

  22. Bytes, Nibbles, and Bits

  23. PLC Data Formats • Two 8-bit unsigned bytes of data • 16-bit unsigned integer • 16-bit signed integer • 32-bit signed integer • Binary coded decimal • Hexadecimal

  24. Two 8-bit Unsigned Bytes of Data

  25. Hexadecimal

  26. 16-bit Signed Integer

  27. 16-bit Unsigned Integer

  28. 32-bit Signed Integer (1 of 2) Double Word Lower 31 bits contain the value Sign bit 32 – bit signed integer data range: -2,147,483,648 to +2,147,483,647

  29. 32-bit Signed Integer (2 of 2) DoubleWord Byte Byte Byte Byte Word Word

  30. Basic PLC Data Types

  31. Data Table Format • Words are 16 bits. • Bits 0 through bit 15 • First word or bit is always 0. • SLC 500 data tables can contain up to 256 words (0 to 255). • PLC 5 data tables can contain up to 1,000 words (0 to 999).

  32. Words Arranged in a Data Table

  33. Status Table Words Assigned by Module Requirements • The number of status table words assigned depend on what a specific module needs. • 16-point module equals 16 bits. • 32-point module equals 32 bits. • Four-channel analog equals four words. • Eight-channel analog needs eight.

  34. SLC 500 I/O Configuration

  35. 16-point Module’s I/O Points Represented in a Word

  36. Physical Input Conditions and the Corresponding Input Data Word

  37. 8-Point Input Module Represented in a Word

  38. SLC 500 Input Status Table

  39. 24-point I/O Module Represented in Two Words

  40. Two Words Representing Inputs for a 32-bit Module

  41. Output Status File Correlation to Module

  42. SLC 500 Digital Outputs

  43. Four Words Representing a Four-channel Analog Module 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 Channel 0 Channel 1 Channel 2 Channel 3

  44. SLC 500 Analog Input Channels

  45. SLC 500 Output Analog Channels

  46. So, What’s in It for ME?? • I need to be able to work with different number systems. • PLC configuration • PLC troubleshooting • Program interpretation • Error code interpretation • Data conversion to different hardware

  47. SLC 500 Analog Input Module Configuration • You need to configure a 1747sc-INI4i analog input module. • Module configuration specifications are listed below.

  48. Channel Configuration Word Channel Data Word SLC 500 Processor Analog Input Module Channel Status Word Analog Input Signal Channel Configuration

  49. Specifications • Enable the input channel • 4- to 20-mA input range • Work in engineering units • Pump to run maximum if open input • 60-Hz input filter • Auto calibration disabled

  50. What Do You Need to Do? • Determine the 16-bit data word for the configuration. • Convert the binary word into decimal. • Program a move instruction on your SLC 500 ladder to move the configuration data to each analog channel.

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