Deck 7: Program Control Instructions

Question 1

Power to the PLC input and output devices are usually controlled by means of a hardwired Master Control Relay circuit.

Answer 1

True

Question 2

The label instruction has a logical true condition.

Answer 2

True

Question 3

The immediate I/O instruction is most useful if the instruction associated with the device is at the beginning of the program.

Answer 3

False

Question 4

The immediate I/O instruction is used with critical I/O devices that require updating in advance of the I/O scan.

Question 5

In a jump-to-label program, the label instruction is used to identify the ladder rung that is the target destination of the JMP instruction.

Question 6

The safest way to wire a stop button to a PLC system is to use an NC contact programmed to examine for an ON condition.

Question 7

The master control relay instruction can be used as a substitute for a disconnect switch.

Question 8

The use of a motor starter seal-in contact in place of a programmed contact provides positive feedback about the exact status of the motor.

Question 9

The forcing capability of a PLC allows the user to turn an external I/O on or off regardless of the state of the device.

Question 10

Master control reset (MCR) and jump (JMP) are often referred to as override instructions.

Question 11

The use of the immediate I/O instruction increases the total scan time of the program.

Question 12

A main disconnect switch is installed on the incoming power lines as a means of removing power from the entire PLC system.

Question 13

The jump-to-subroutine instruction is used where a machine has a portion of its cycle that must be repeated several times during one machine cycle.

Question 14

When the MCR instruction is true, all rung outputs below the MCR will be controlled by their respective input conditions.

Question 15

The label address must match that of the JMP instruction with which it is used.

Question 16

Random forcing of given inputs or outputs can cause equipment damage.

Question 17

When the program scan reaches an immediate I/O instruction, the scan is interrupted and the bits of the addressed word are updated.

Question 18

Emergency stop circuits should be hardwired outside of the controller program so that, in the event of total controller failure, independent and rapid shutdown means are available.

Question 19

The MCR instruction can only be programmed to control an entire circuit.

Question 20

The JMP instruction does not contribute to logic continuity and, for all practical purposes, is always logically true.

Question 21

When the MCR instruction is false, output(s) ____ will always be de-energized.

A)M, PL1 and SOL
B)M and PL1
C)PL1
D)SOL

Question 22

Each JMP instruction must have a LBL instruction.

Question 23

The fault routine allows for an orderly shutdown in case of a fault.

Question 24

The MCR instruction is not a replacement for a hardwired master control relay that provides emergency stop.

Question 25

Which of the following PLC instructions would not be classified as an override instruction?

A)Master control reset
B)Jump-to-subroutine
C)Output energize
D)Jump-to-label

Question 26

You must de-energize the JMP instruction to activate it.

Question 27

Forcing outputs affects only the addressed output terminal.

Question 28

Programming the selectable timed interrupt is done when a section of program needs to be executed on a time basis rather than on an event basis.

Question 29

Nesting subroutines allow you to direct program flow from the main program to a subroutine and then to another subroutine.

Question 30

When programming MCR instructions, the first rung has a conditional MCR output instruction and the last rung is an unconditional MCR rung.

Question 31

The JMP instruction allows a section of a program to be jumped when a production fault occurs.

Question 32

When an MCR zone goes false, off-delay timers within the zone will automatically activate and begin their off delay cycle.

Question 33

The MCR instruction establishes a zone in the user program in which all nonretentive outputs can be:

A)turned on simultaneously.
B)turned off simultaneously.
C)turned on in a defined sequence.
D)turned off in a defined sequence.

Question 34

A latch instruction will automatically unlatch if it is contained within a de-energized MCR zone.

Question 35

Jumping to a subroutine does not cause any rungs of the main program to be skipped over.

Question 36

You must energize the MCR instruction to activate it.

Question 37

Assume that the MCR instruction makes a false-to-true transition. As a result:

A)all outputs will be controlled by the respective input conditions.
B)all nonretentive outputs will de-energize.
C)all retentive outputs will de-energize.
D)all nonretentive outputs will energize.

Question 38

It is not possible to jump backward in the program.

Question 39

Nested subroutines make complex programming easier.

Question 40

The temporary end instruction, when true, stops the program scan.

Question 41

The fenced zone controlled by the MCR instruction is (are):

A)rungs No.1 through No.8.
B)rungs No.3 through No.6.
C)rungs No.2 and No.6.
D)rung No.2.

Question 42

Immediate instructions are most useful when programmed:

A)immediately after the I/O scan has occurred.
B)immediately prior to the I/O scan.
C)at the middle or toward the end of the program.
D)near the beginning of the program.

Question 43

The use of immediate instructions:

A)increases the total scan time of the program.
B)decreases the total scan time of the program.
C)increases the number of rungs that can be programmed.
D)decreases the number of rungs that can be programmed.

Question 44

When the jump-to-label instruction is executed, the outputs of the jumped rungs:

A)are all energized.
B)are all de-energized.
C)are all immediately updated.
D)remain in their last state.

Question 45

The immediate input and output instructions provide a way of:

A)ending the program immediately.
B)restarting the program immediately.
C)temporarily interrupting the program scan to allow selected bits in the data table to be updated.
D)temporarily interrupting the program scan to reset all bits in the data table to zero.

Question 46

Forcing functions are often used:

A)to continue a machine process until a faulty field device can be repaired.
B)for testing purposes during an initial start-up.
C)for troubleshooting purposes.
D)all of these.

Question 47

Immediate instructions should be used only when:

A)a program must be halted immediately.
B)a program must be restarted immediately.
C)the updating of an input or output is critical to your operation.
D)the resetting of all bits in the data table is critical to your operation.

Question 48

Which output is not affected by the JMP instruction?

A)M
B)SOL 1
C)SOL 2
D)PL2

Question 49

The forcing function of a PLC allows the user to turn an external input or output on or off:

A)according to the forced program.
B)according to the main program.
C)from the keyboard regardless of its actual status.
D)all of these.

Question 50

The latch and unlatch instructions would be classified as:

A)retentive outputs.
B)nonretentive outputs.
C)condition instructions.
D)unconditional instructions.

Question 51

The label (LBL) instruction:

A)is always logically true.
B)has the same address as the JMP instruction with which it is used.
C)is used to identify the ladder rung that is the target destination of the JMP instruction.
D)all of these.

Question 52

Assume output SOL C is energized at the time the MCR instruction makes a true-to-false transition. As a result, output SOL C will:

A)de-energize.
B)remain energized.
C)remain energized but still be controlled by inputs LS3 and LS4.
D)de-energize but still be controlled by inputs LS3 and LS4.

Question 53

Assume the alarm output is activated. This would require the:

A)temperature switch input to be true.
B)manual Automatic input to be true.
C)LS4 input to be true.
D)temperature switch input and Manual Automatic input to be true.

Question 54

Which of the following instructions would most likely be programmed outside the jumped area of a program?

A)Latch and unlatch instructions
B)Timer and counter instructions
C)Immediate inputs and outputs
D)Forced inputs and outputs

Question 55

The jump-to-subroutine instruction can save a great deal of duplicate programming in cases:

A)that require the programming of several timers.
B)that require the programming of several counters.
C)where a machine has a portion of its cycle that must be repeated several times during one machine cycle.
D)all of these.

Question 56

When the processor scan reaches the RET instruction, it will return the processor to the:

A)start of the program.
B)end of the program.
C)rung above the JSR instruction.
D)rung below the JSR instruction.

Question 57

Which of the following is the conditional instruction that controls the MCR zone?

A)Stop
B)Start
C)Manual Automatic
D)Temperature Switch

Question 58

Rungs 5, 6, and 7 are not scanned by the processor when rung ____ has logic continuity.

A)1
B)2
C)3
D)4

Question 59

The main advantage to the jump-to-label instruction is that:

A)any number of rungs may be programmed between the jump and label rungs.
B)it allows you to use one set of condition instructions to control multiple outputs.
C)it allows you to use one set of condition instructions to control multiple inputs.
D)it has the ability to reduce the processor scan time.

Question 60

When the examine on sensor instruction is true, the processor:

A)turns on all outputs in the subroutine area.
B)turns off all outputs in the subroutine area.
C)stops executing the subroutine.
D)starts executing the subroutine.

Question 61

The actual status of output address 0:2/5 is ____, but the forced status is ____ .

A)false ...true
B)true ...false
C)false ...false
D)true ...true

Question 62

The output of 0:2/5 would be ____ and the output of 0:2/6 would be ____ .

A)false ...true
B)true ...false
C)false ...false
D)true ...true

Question 63

The ____ is the target for the JMP instruction.

A)LBL
B)TND
C)IOT
D)RET

Question 64

Assume that the stop button was changed to a normally open contact type. As a result, the program could be made to operate as before by changing the instruction at address:

A)stop to examine if open.
B)start to examine if open.
C)starter auxiliary contact to examine if open.
D)stop to examine if open and starter auxiliary contact to examine if open.

Question 65

PLC emergency stop circuits should be:

A)hardwired outside the controller program.
B)programmed as part of the MCR instruction.
C)programmed as part of the zone control last state instruction.
D)programmed as an immediate input instruction.

Question 66

When replacing modules or working on equipment controlled by the PLC installation, the safest way to proceed is to:

A)de-energize the MCR coil.
B)block open the emergency stop switch.
C)remove the fuse from the circuit.
D)pull and lock the disconnect switch.

Question 67

A JSR instruction:

A)tells the processor to jump from the main program to a subroutine area or file.
B)tells the process to execute the fault routine.
C)latches outputs when energized.
D)latches outputs when de-energized.

Question 68

Power to the processor module is controlled by the:

A)master control relay.
B)start/stop buttons.
C)main disconnect switch.
D)All of these choices are correct

Question 69

The ____ instruction stops the processor from scanning the rest of the program.

A)LBL
B)IOT
C)TND
D)STI

Question 70

The use of the starter auxiliary contact instead of a programmed contact:

A)is more costly.
B)is safer.
C)provides positive feedback about the exact status of the motor.
D)all of these.

Question 71

A JMP instruction is similar to a(n):

A)MCR command.
B)ZCL command.
C)skip command.
D)JSR command.

Question 72

The transformer is used to:

A)isolate the controller from the main power lines.
B)step up the main power line voltage.
C)provide the low-voltage do operating voltage for the controller.
D)All of these choices are correct

Question 73

Assume the processor comes equipped with a normally closed fault relay contact output designed to open when a processor malfunction is detected. This contact would be:

A)programmed as part of the MCR instruction.
B)programmed as part of the zone control last state instruction.
C)hardwired in series with the emergency stop button.
D)hardwired in parallel with the emergency stop button.

Question 74

The actual status of input 1:1/3 is ____ but the forced status is ____.

A)false ...true
B)true ...false
C)false ...false
D)true ...true

Question 75

Forcing functions should not be used:

A)with retentive outputs.
B)with nonretentive outputs.
C)with immediate I/O instructions.
D)without consideration for any potential unsafe effects.

Question 76

The status of examine on instruction 0:2/5 would be ____ and the status of output 0:2/6 would be ____ .

A)false ...true
B)true ...false
C)false ...false
D)true ...true

Question 77

The MCR instruction:

A)is an output instruction.
B)is used in pairs.
C)is used to disable or enable a zone within a ladder program.
D)all of these.

Question 78

Assume that the NC stop button is replaced with an NO stop button and that the program is changed so it operates as before. Should the field wire connected to one end of the stop button break off:

A)the motor would stop automatically.
B)pressing the stop button would stop the motor.
C)pressing both the start and stop buttons would stop the motor.
D)none of these.

Question 79

Power to the input and output module is controlled by the:

A)master control relay.
B)start/stop buttons.
C)main disconnect switch.
D)All of these choices are correct

Question 80

The ____ instruction will return the scan to your main program at the completion of the subroutine.

A)LBL
B)IIN
C)TND
D)RET