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ECT 464

ECT 464. Lecture 5 Modes and Memory. Do the thing you fear and the death of fear is certain. Be strong and courageous. Do not be afraid or terrified because of them, for the LORD your God goes with you; he will never leave you nor forsake you. Deuteronomy 31:6. PLC Modes of Operation. Run

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ECT 464

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  1. ECT 464 Lecture 5 Modes and Memory

  2. Do the thing you fear and the death of fear is certain. Be strong and courageous. Do not be afraid or terrified because of them, for the LORD your God goes with you; he will never leave you nor forsake you. Deuteronomy 31:6

  3. PLC Modes of Operation • Run • Program • Troubleshoot

  4. Program Mode • All outputs off • I/O scan is off • Upload/Download programs from PLC • Monitor and Edit programs, ladder logic, rung descriptions • Set I/O force bits without enables being executed

  5. Run Mode • Scans Inputs, stores in memory • Scans Rungs, sets outputs in memory • Sets Outputs

  6. PLC Scan Time • The time it takes to complete one complete cycle in run mode. • Can take milliseconds depending on number of rungs in ladder logic • Inputs must stay enabled for one scan cycle period

  7. Internal File Structure • Program File • Data File • Function File • Specialty File

  8. Program File • 0 and 1, processor, passwords, I/O • 2 ladder program • 3 to 255 subroutines

  9. Data File • 0 O output output data bits to be copied to I/O • 1 I input input data bits from I/O • 2 S status processor status bits • 3 B bit 256 words with 16 bits each 4096 individual bits • 4 T timer 256 words 84 timer instructions • 5 C counter 256 words 84 counter instructions • 6 R control 256 words 84 instructions • 7 N integer 256 words for storage • 8 F Floating Point • 9 reserved Network communications • 10-255 extra storage for any type. However once you start it on one type it is set.

  10. Extra Data File Types • ST String • L Long Word • MG Message • PD PID • PLS Programmable Limit Switch

  11. Function File Types

  12. Specialty File Types

  13. Addressing Modes • Element Address N7:15 • used to access a word at a time (integer or control) • Word Address T4:5.PRE • used to access a word at a time (timer, counter, or control) • Bit Address B3:01.11 or B3/27 • used to access a bit at a time

  14. Addressing Details

  15. Addressing Details

  16. Addressing Examples

  17. Addressing Modes • I:7/8 • O:5 • S:1/15 • B3:252/0 • R6:2/9 • N7:2 • T4:0.ACC • C5:244.PRE

  18. Other Addressing Modes • I:3.1/3 • O:5.0/2 • S:32/3 (32 max) • B10/4095 (4095 max) • R15:2/FD • N255:2/8 (255 max) • T40:0/TT • C55:244/OV

  19. Indirect Addressing Mode • N7:[N10:1] • N[N50:1]:10 • B3/[B25:0]

  20. PLC wiring • PLC output power through E-Stop for Diagnostics and not as input in case of frozen PLC • Keep 24V away from 120V and motors • Try to keep noise to a minimum

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