Rob t 308 Lecture 18

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ROBT 308Industrial Automation

Lecture 18

– Data manipulation instructions (part b)

– Math Instructions

17 March 2015, Tuesday

Industrial Automation (ROBT308) - Spring 2015

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Topics

2

Today’s Topics

File arithmetic and logic (FAL) instruction

File copy (COP) instruction and the fill file (FLL)

Data comparison instructionsData Manipulation Programs

Numerical Data I/O Interfaces

Closed loop Control

Math Instructions (Addition, Subtraction, Multiplication,Division)

File Arithmetic Operations

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Industrial Automation (ROBT308) - Spring 2015 3

A file is a group of related consecutive words in

the data table that have a defined start and end

and are used to store information.Moving data using file instructions

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Address #N7:30 represents the starting address of

a group of consecutive words in integer file 7.

The length is eight words, which is determined by the

instruction where the file address is used.


SLC 500 word and file addressing.

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The file arithmetic and

logic (FAL) instruction is

used to copy data fromone file to another and to

do file math and file logic.

Control word uses four control bits: enable bit, done bit, error bit,

and unload bit.

Length represents the file length in words.

Position points to the word being operated on.

Mode (All, Numeric or Incremental) represents the number of file

elements operated on per program scan.

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Destination is the address at which the processor stores theresult of the operation.

Expression contains addresses, program constants, and operators

that specify the source of data and the operations to beperformed. The expression entered determines the function of

the FAL instruction.

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File-to-file copy function program using the FAL

instruction.

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File-to-word copy function using the FAL

instruction.

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Word-to-file copy function using the FAL

instruction.

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Copying recipes and storing values for timer

presets.

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The file copy (COP) instruction and the fill file (FLL)

instruction are high-speed instructions that operate

more quickly than the same operation with the FALinstruction.

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There is no control element to monitor and data

conversion does not take place, so the source and

destination should be the same file types.

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Using the FLL instruction to change all the data in

a file to zero.

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Data Compare Instructions

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Comparison instructions are used to test pairs of

values to determine if a rung is true.

LIM (Limit test) —Tests whether one value is within the limitrange of two other values.

MEQ (Masked Comparison for Equal) —Tests portions of two

values to see whether they are equal.

Compares 16-bit data of a source address to 16-bit data at areference address through a mask.

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EQU (Equal) —Tests whether two values are equal.

NEQ (Not Equal) —Tests whether one value is not equal to a

second value.

LES (Less Than) —Tests whether one value is less than a

second value.GRT (Greater Than) —Tests whether one value is greater than

a second value.

LEQ (Less Than or Equal) —Tests whether one value is less

than or equal to a second value.

GEQ (Greater Than or Equal) —Tests whether one value isgreater than or equal to a second value.

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The equal (EQU) instruction rung compares the

value of source A to that of source B.

When source A is equal to source B, the instruction is logically

true and PL1 is switched ON.

When source A is not equal to source B, the instruction is logically

false and PL1 is switched OFF.

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The not equal (NEQ) instruction is logically true

when source A is not equal to source B, otherwise

it is logically false.

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The greater than (GRT) instruction is logically

true when source A is greater than source B,

otherwise it is logically false.

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The less than (LES) instruction is logically true when

source A is less than source B, otherwise it is

logically false.

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The greater than or equal (GEQ) instruction is

logically true when source A is greater than or

equal to source B, otherwise it is logically false.

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The limit test (LIM) instruction is used to test

whether values are within or outside the

specified range.

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The low limit is less than the high limit.

Instruction is true for test values 25 through 50.

Instruction is false for test values less than 25 or greater than 50.

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Instruction is true for test values of 50 and less than 50 and for

test values of 100 and greater than 100.

Instruction is false for test values greater than 50 and less than

100.

The low limit is greater than the high limit.

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The masked comparison for equal (MEQ)

instruction compares a value from a source

address with data at a compare address andallows portions of the data to be masked.

The MEQ instruction can be used to compare the correct position of

up to 16 limit switches when the source contains the limit switch

address and the compare stores their desired states.

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MEQ instruction rung.

When the data at the source address match the data at the

compare address bit-by-bit (less masked bits), the instruction is

true.

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Data Manipulation

Programs

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Hardwired relay-operated, time-delay circuit.

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Equivalent programmed time-delay circuit.

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Timer program implemented using the EQU

instruction.

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Counter program implemented using the LES

instruction.

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Vessel filling

operation.

ØThe receiving vessel has its weight

monitored continuously by the PLC

program as it fills.

ØWhen the weight reaches a preset

value, the flow is cut off.

ØShould the system leak additional material into the vessel, the

total weight of the material could rise above the preset valuecausing an equal instruction, if used, to go false and the vessel to

overfill.

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Numerical Data I/O

Interfaces

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Multibit interfaces allow a

group of bits to be input or

output as a unit.Each one of the switches provides four

binary digits at its output that

correspond to the decimal number

selected on the switch.

The BCD input module allows the

processor to accept the 4-bit digital

codes and input their data into

specific register or word locations.

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The seven-segment LED display

is a typical Binary Coded

Decimal output device.

It displays a decimal number that

corresponds to the BCD value it receives

at its input.

The BCD output module is used to

output data from a specific register orword location.

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Program for monitoring the setting of a

thumbwheel switch.

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Analog modules convert analog signals to 16-bit

digital signals (input) or 16-bit digital signals to

analog values (output).

An analog I/O will allow

monitoring and control ofanalog voltages and currents.

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The analog output interface module receives

numerical data from the processor.

These data are then translated into a proportional

voltage or current to control an analog field

device.

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In open-loop control , no feedback loop is

employed and system variations which cause the

output to deviate from the desired value are notdetected or corrected.

A closed-loop system utilizes feedback to

measure the actual system operating parameter

being controlled.

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PLC closed-loop control system.

Adjustments are

made continuously

by the PLC until the

difference between

the desired andactual output is as

small as is practical.

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Proportional controls are designed to eliminate the

hunting or cycling associated with on/off control.

Proportional control

allows the control

element to take

intermediatepositions between

on and off.

The PLC analog output module controls the amount of fluid flow by

adjusting the percentage of valve opening.

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Proportional-integral-derivative (PID) control is

the most sophisticated and widely used type of

process control.

PID controllers produce outputs that depend on the magnitude, duration, and

rate of change of the system error signal.

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PID control loop

ØOperating information from the machine is called the process variable or

feedback.

ØInput from the operator that tells the controller the desired operating point is

called the set-point .

ØThe difference between the set-point and the process variable is called the

error.

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Programmable controllers are either equipped

with PID I/O modules that produce PID control or

have sufficient mathematical functions of theirown to allow PID control to be carried out.

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Math Instructions

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The PLC’s math functions capability allows it to

perform arithmetic functions on values.

Addition - The capability to add one piece of data to another.Subtraction - The capability to subtract one piece of data from

another.

Multiplication - The capability to multiply one piece of data by

another.

Division - The capability to divide one piece of data by another.

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When the CPT (compute)

instruction is executed, then

copy, arithmetic, logical, orconversion operation residing

in the expression field of this

instruction is performed and

the result is sent to thedestination.

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Addition Instruction

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The ADD instruction performs the addition of two

values stored in the referenced memory locations.

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Counter program that uses the ADD instruction.

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The arithmetic status bits

for the SLC 500 are found in

word 0, bits 0 to 3 of the

processor status file S2.

Carry (C) - Address S2:0/0, is set to 1 when there is a carry in the

ADD instruction or a borrow in the SUB instruction.

Overflow (O) -Address S2:0/1, is set to 1 when the result is too

large to fit in the destination register.

Zero (Z) - Address S2:0/2, is set to 1 when the result of the subtract

instruction is zero.

Sign (S) - Address S2:0/3, is set to 1 when the result is a negative

number.

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Subtraction Instruction

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The subtract instruction subtracts source B from

source A and stores the result in the destination.

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Vessel overfill alarm program.

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Multiplication Instruction

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MUL instruction program used to calculate the

product of two sources.

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The MUL

instruction

used as part

of atemperature

control

program.

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Division Instruction

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The division instruction divides the value in source

A by the value in source B and stores the result in

the destination address.

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DIV instruction used to calculate the value that

results from dividing source A by source B.

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Program for

converting

Celsius

temperature toFahrenheit.

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Other Word-Level Math

Instructions

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Square root instruction.

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The negate (NEG) instruction changes the sign of

the source value from positive to negative.

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The clear (CLR) instruction sets all bits of a word to

zero.

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The scale data (SCL) instruction is used to allow

very large or very small numbers to be enlarged

or reduced by the rate value.

The number 100 stored at the

source address, N7:0, is multiplied

by 25,000, divided by 10,000, and

added to 127.

The result, 377, is placed in the destination address, N7:1.

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File Arithmetic Operations

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The file subtract function of the FAL

instruction is used to perform subtraction

operations on multiple words.

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The file multiplication function of the FAL

instruction is used to perform multiplication


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The file divide function of the FAL

instruction is used to perform division


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Rob t 308 Lecture 18

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