ECT 464

1
ECT 464

• Lecture 4b
• Special Functions

2
Special Functions

• One Shot (ONS) (OSR) SLC500
• triggers a one time event
• activates on false to true transition
• rung must go false again to reset
• allowed to use one OSR per output in a rung
• do not place input conditions after the OSR
• uses a bit location to store last state

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Special Functions

• One Shot Rising (OSR)
• triggers a one time event
• activates on false to true transition
• rung must go false again to reset
• allowed to use one OSR per output in a rung
• do not place input conditions after the OSR
• uses a bit location to store last state
• Activates output bit

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Special Functions

• One Shot Falling (OSF)
• triggers a one time event
• activates on true to false transition
• rung must go true again to reset
• allowed to use one OSF per output in a rung
• do not place input conditions after the OSF
• uses a bit location to store last state
• Activates output bit

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Special Functions

• Label (LBL)
• Target of jump instruction
• Must be first instruction of rung
• 256 labels in each subroutine (SLC)
• 1000 labels in each subroutine (M1000)

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Special Functions

• Master Control Reset (MCR)
• Acts on rungs between start and end fence
• When off, ignores inputs, and de-energizes all
  outputs in the zone
• When on, inputs and outputs treated normally
• Latches, retentive timers, and counters remain in
  their last state
• Must end zone with unconditional MCR
• Cannot nest MCRs
• Always place MCR as last instruction on rung

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Special Functions

• Jump (JMP)
• When true, skips to the rung with the LBL
  instruction and continues executing
• When false, doesnt do anything
• Can jump forward and backward
• Can jump to the same label from several JMP
  instructions
• Do not jump into a MCR zone
• Not between program files

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Special Functions

• Temporary End (TND)
• Stops processor from scanning the rest of the
  rungs
• Used to debug a program
• Used to stop the execution of part of a main
  program or subroutine

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Special Functions

• Suspend (SUS)
• Sends PLC into idle mode
• All outputs de-energized
• Used with Suspend ID number

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Special Functions

• Subroutine (SBR)
• Marks the beginning of a file
• Optional use

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Special Functions

• Jump to Subroutine (JSR)
• Used to execute a subroutine and then return
• Saves memory
• Nest 8 levels deep
• File number 3-255 (SLC or M1500)
• File number 4-15 (M1000)

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Special Functions

• Return (RET)
• Marks the end of a subroutine
• Can be conditional (SLC)
• Optional Use (END works as well)
• Can return a value (SLC)

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Special Functions

• End (END)
• Marks the end of a file

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Special Functions

• Immediate Input with Mask (IIM)
• Update data prior to normal scan
• Mask of 1 passes
• Specify input word
• Embedded I/O only

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Special Functions

• Immediate Output with Mask (IOM)
• Update outputs prior to normal scan
• Mask of 1 passes
• Specify output word
• Embedded I/O only

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Special Functions

• I/O Refresh (REF)
• Executes a new I/O scan in middle of execution
• Can also do communications

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Next Class

• I/O Scans and memory layout
• PLC Modes