05 programming relay bit instructions Training PLC Allen Bradley

• Explain the function and programming of the coil output energize, OTE, latch output latch, OTL and unlatch output unlatch, OTU instructions • Logic-type Instruction: • Explain the fun

• Explain the function and programming of the coil (output energize,

OTE), latch (output latch, OTL) and unlatch (output unlatch, OTU)

instructions

• Logic-type Instruction:

• Explain the function of the AND instruction

• Explain the function of the NOT instruction

• Explain the function of the OR instruction

The input image file in the processor stores the status of input

sensors connected to input module terminals

The output image file controls the status of actuators wired to

output module terminals

I/O IMAGE FILES IN DATA STORAGE

If the Input Sensor Is: Then Its Corresponding Input Image Bit Is:

closed (on) on (1)

open (off) off (0)

If the Input Sensor Is: Then Its Corresponding Input Image Bit Is:

closed (on) on (1)

open (off) off (0)

RUNG LOGIC

• As each conditioning instruction is executed, the addressed

bit is examined to see if it matches a certain condition (on or

off)

• If a complete path of true conditions examined for are found,

the rung is set to true

• The rung must contain a continuous path of true instruction

from the start of the rung to the output for the output to be

enabled

Power Rail

Ladder Logic can contain conditional input instruction

and output instructions An example of a rung of Ladder

Logic is shown in the following graphics

( )

] [ ] [ ] [

Conditional Input Instruction

Output Instruction

BIT INSTRUCTIONS

Use the bit(relay-type) instructions to monitor and control the

status of bits.

ONS XIO

XIC

OSR OSF

OTL OTU OTE -7

BIT INSTRUCTIONS TYPES

EXAMINE IF CLOSE (XIC)

The XIC instruction examines the data bit to see if it is set

Examine data bit

EXAMINE IF OPEN (XIO)

The XIC: examines the data bit to see if it is cleared.

Examine data bit

OUTPUT ENERGIZE (OTE)

When OTE is enabled, controller sets data bit When OTE is disabled,

controller clears data bit.

Rung Condition Data Bit

OUTPUT LATCH (OTL)

When enabled, OTE sets data bit Data bit remains sets until cleared,

typically by OTU When disabled, does not change status of data bit.

Rung Condition Data Bit

OUTPUT UNLATCH (OTU)

When enabled, OTU clears data bit When disabled, does not change

status of data bit.

Rung2 Condition

Data Bit (light_2)

Rung 1

Rung 2

Rung1 Condition

ONE SHOT (ONS)

When enabled and storage bit is cleared, ONS enables the reminder of

the rung When disabled or storage bit is set, ONS disables the reminder

of the rung.

Switch_1 Switch_0

ONE SHOT RISING (OSR)

When enabled and storage bit is cleared, OSR sets output bit When

enabled and storage bit is set or when disabled, OSR clears output bit

Storage Bit

Add Switch_1

ONE SHOT FALLING (OSF)

When disabled and the storage bit is set, the OSF instruction sets

the output bit When storage bit is cleared, or when enabled, the

OSF instruction clears the output bit.

Storage Bit Switch_0

BOOLEAN LOGIC PROGRAMMING

A PLC can do nothing without a (ladder logic) program in it

The process of converting control objectives into a ladder logic

program requires:

• details of the process operations

• structured thought

• solid basic logic understanding

Boolean algebra provides the tools needed to analyze and design

these systems

• Developed in the 1800’s by James Bool, an Irish mathematician

• Can model logical systems with equations which can then be simplified

and/or manipulated into new forms

• The variable for these equations can ONLY have a value of 0 for false, or

1 for true

• Adapt very well to ladder logic programming

BOOLEAN EQUATIONS

Consist of variables and operations and look very similar to

normal algebraic equations

The AND’s truth table

Normally open, N.O.

Fig N.O instruction

Fig Normally closed, N.C, instruction

Boolean equation