SEQUENCE CONTROL (SEQUENCE TABLE)

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SEQUEN CE CON TROL

( SEQUEN CE TABLE)

PT. Yo ko g a wa Indo ne sia

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The following funct ion blocks are cat agorized as sequence

cont rol blocks:

1.

Sequence Table Blocks

2.

Logic Chart Block

3.

Sequent ial Funct ion Chart Block

4.

Swit ch I nst rum ent Blocks

5.

Sequence Elem ent Blocks

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This funct ion blocks realizes sequence cont rol by operat ing ot her funct ion blocks and/ or

pr ocess or soft ware I / O.

Ther e are t w o basic t ype of Sequence Table blocks:

•

Sequence Table Block ST16

•

Rule Ex t ension Block ST16E

On t op of t he basic t ypes above, t her e are also ot her t ypes such as



Sequence Table Block M_ST16

( Num ber of condit ion signals: 32 t o 64, num ber of act ion signals: 32 t o 64 / Tot al 96)



Rule Ex t ension Block M_ST16



Sequence Table Block L_ST16

( Num ber of condit ion signals: 64, num ber of act ion signals: 64 / Tot al 128)



Rule Ex t ension Block L_ST16

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Sequence Table block ( ST16, ST16E) is a decision t able t ype funct ion block t hat describes

t he relat ionship bet w een input signal and out put signal in a

Y/ N ( Ye s/ N o)

fashion.

The ST16 block has a sequence cont rol funct ion t hat handles a t ot al of 64 I / O signals and 32

rules. The I / O signals can also be redist ribut ed in t he 8- signal unit .

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When t he phase st ep sequence t able is used, t he num ber of processes ( num ber of st eps)

m ay be insuficient depending on t he process t hat is being perform ed.

Solu t ion

: use t he rule expansion form at sequence t able block ( ST16E) t o expand t he

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Con figu r a t ion

•

Con dit ion Sign a l

Ent er t he elem ent sym bol in t he

Tag Nam e Dat a

I t em

colum n ( eg.

FC002.ALRM

) and condit ion

specificat ion in t he

Dat a

colum n ( eg.

HI

) .

•

Act ion Sign a l

Ent er t he elem ent sym bol in t he

Tag Nam e Dat a

I t em

colum n

( eg. % AN0010.PV)

and act ion

specificat ion in t he

Dat a

colum n (

eg. H

)

.

•

Ru le N u m be r

Up t o 32 rules per block m ay be used. The

out put is based on each rule condit ion and

condit ion t est ing result .

•

Con dit ion Ru le

Use

Y/ N

pat t ern ( in com binat ion) t o condit ion

rule. I f t he t est ing result of condit ion signal

corresponds w it h t he

Y/ N

pat t ern, t he condit ion

is t hen said sat isfied.

•

Act ion Ru le

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Con figu r a t ion

•

St e p La be l

St ep labels are used for phase indicat ion when

perfor m ing st ep sequence cont r ol in t he

Sequence Table. The labels are charact er st r ings

t hat com bine t w o or less alphanum eric

charact ers ( A t o Z, 0 t o 9) .

•

N e x t St e p La be l

TH EN

Execut e t he next st ep label when t he

corresponding rule condit ion st at us is t rue or

sat isfied & aft er t he m anipulat ed out put is

com plet ed.

ELSE

Execut e t he next st ep label when t he

corresponding rule st at us is false.

•

Ta g N a m e .D a t a I t e m

Describe t he connect ion inform at ion of t he

condit ion and act ion signal ( eg.

FC001.MODE,

FC001.PSW, TI MER001.OP

, et c) .

•

D a t a

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Con figu r a t ion

•

Com m e n t

Com m ent s are defined by user t o descr ibe t he m eaning

of sym bols & cont ent s of st at us m anipulat ion of

condit ion & act ion rules.

•

Pr oce ssin g Tim in g

There ara t wo processing t im ings:

St a r t / Ex e cu t ion Tim in g

I t refers t o t he t im ing at w hich cont r ol algor it hm s are

execut ed when receiving input signals. Select one of t he

follow ing t ype

-

Periodic Execut ion

( T)

-

One- Shot Processing

( O)

-

St art up at I nit ial Cold St art / Rest art of FCS

( I )

-

Rest rict ed I nit ial Execut ion

( B)

Out put Tim in g

I t indicat es t he condit ion or behaviour of act ion signals

in conj unct ion w it h t he condit ion rule st at us change

( applicable w it h T & O t ype of

St art Tim ing

only) .

Select eit her

-

Out put Only When Condit ion Change

( C) or

-

Out put Each Tim e Condit ions Are Sat isfied

( E)

•

Sca n Pe r iod

Sequence t able wit h per iodic execut ion t ype ( T) is

act ivat ed at defined scan period.

There are t hree t ypes of scan periods:

--

Basic Scan ( 1 second

–

fixed)

--

Medium Speed Scan ( 200 & 500 m illiseconds)

50, 100, 250 m illiseconds are also applicable.

--

High Speed Scan ( 200 & 500 m illiseconds)

50, 100, 250 m illiseconds are also applicable.

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St art / Execut ion Tim ing

Periodic Execut ion ( T)

The periodic execut ion m eans t hat t he sequence cont rol block is repeat edly execut ed in a

preset cycle.

One

-

Shot Execut ion ( O)

When execut ion t im ing of a funct ion block is defined as one- shot t ype, t he block is execut ed

only w hen it is invoked by ot her funct ion block. A one- shot funct ion block can invoke anot her

one- shot funct ion block. How ever, such succession is lim it ed t o seven blocks. I nvocat ion can

only be init iat ed from t he sam e FCS.

I nvoking funct ion

block

One- shot t ype

funct ion block

I nvocat ion signal

Sequence process execut ion

ACT.OFF

ACT.ON

I dle

Execut ing

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St art / Execut ion Tim ing

I nit ial Execut ion/ Rest art Execut ion ( I )

I n t his execut ion t ype, t he sequence block execut es it s process w hen t he FCS perform s a cold

st art or a rest art .

Rest rict ed I nit ial Execut ion ( B)

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Out put Tim ing

Out put Only When Condit ions Are Changed ( C)

The sequence t able blocks out put an operat ion/ act ion signal only at t he t im ing w hen t he

j udged condit ions are changed from false t o t rue. This is applicable only wit h periodic

execut ion ( T) or one- shot st art ( O) st art t im ing.

Condit ion rule

change

Act ion rule

change

Act ion change/ int erupt ion is

possible event hough t he

condit ions rule are sat isfied

False

True

False

True

“Out put On ly W he n Con dit ions Ar e Cha n ge d” Con ce pt ua l Figu r e

Condit ion det ect ion

( a

ch a nge

from false t o t rue st at e)

N ot e

:

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Out put Tim ing

Out put Each Tim e Condit ions Are Sat isfied ( E)

The sequence t able blocks out put it s operat ion/ act ion signal every scan period as long as t he

j udged condit ions are sat isfied.

Condit ion rule

change

Act ion rule

change

Act ion change/ int erupt ion is

n ot

possible as long as t he

condit ion rem ains sat isfied.

False

True

False

True

“Out put Ea ch Tim e Con dit ions Ar e Sa t isfie d” Con ce pt ua l Figu r e

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Sequence Descript ion Exam ple ( AND Gat e)

The basic logical AND gat e can be configured in a Sequence Table

as follow :

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Sequence Descript ion Exam ple ( OR Gat e)

The basic logical OR gat e can be configured in a Sequence Table

as follow :

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Operat ion Of Non- St ep Sequence

I n a non st ep sequence t able, all 32 rules are subj ect t o condit ion t est ing and t he

out put operat ion is perform ed according t o t he condit ions.

As for condit ion t est ing, a condit ion is

sat isfied w hen all condit ions ( Y/ N) for t he

sam e rule num ber are t rue. Rule colum n

t hat is blank is considered t rue

uncondit ionally.

Operat ions/ act ions are execut ed according

t o t he operat ion cont ent s of Y/ N pat t erned

for t he rule num ber w hose condit ions are

sat isfied.

When t he condit ions of m ult iple rules are

sat isfied sim ult aneously w it h respect t o

t he sam e act ion signal, if request for bot h

Y/ N are det ect ed as t he result ant

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Operat ion Of Non- St ep Sequence ( Exam ple)

Here is an exam ple of t he sequence t hat norm ally

m onit ors operat ion t o prevent t he buffer t ank in t he

processing piping syst em from overflow . The sequence

t able below m onit ors t he condit ions in rule num bers 01

t o 04 sim ult aneously. I f any condit ion becom es t rue,

t he act ion/ operat ion in t he sam e rule w ill be execut ed.

The m onit oring cont inues aft er t he execut ion.

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Operat ion Of St ep Sequence

I n a st ep sequence t able, t he process cont rol sequence of a phase- st ep process is divided int o t he

sm allest phase unit s ( st eps) on t he condit ion m onit oring and operat ion, t hen t hese st eps are

execut ed one by one.

Only st ep label 00 and t he rule corresponding t o t he

current st ep num ber are subj ect t o condit ion t est ing &

operat ion.

St ep label 00 is execut ed during each period & it m ay

only be used at t he head of a sequence t able group. So

it cannot be used as a next st ep label.

The next execut ion st ep label m ust be described in

THEN/ ELSE part in order t o advance t he next st ep. I f

bot h are left blank t he sam e st ep is execut ed each t im e

& w ill not advance.

The next st ep specified in THEN part is t he st ep t o

advance w hen t he condit ion t est result is sat isfied ( t rue

st at e) .

The next st ep specified in ELSE part is t he st ep t o

advance w hen t he condit ion t est result is unsat isfied

( false st at e) . I t w ill proceeds t o t he next st ep w it hout

execut ing t he act ion/ operat ion rules.

I f t here are m ult iple request s for st ep t ransit ion in t he

sam e st ep, t he st ep advances t o t he next st ep label

w it h t he sm allest rule num ber.

The next st ep execut ion is done during t he next scan

Only t he act ions for t he rules w hose condit ions are sat isfied in t he st ep current ly being execut ed, are in operat ion.

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Operat ion Of St ep Sequence ( Exam ple)

Se qu e n ce Spe cifica t ion

1. Push t he st art but t on



Valve A opens t o fill t he t ank w it h w at er.

2. When t he t ank is full



Sw it ch A becom es ON.



Valve A is closed.

3. Push t he st art but t on again ( w it h t he t ank full of w at er)



Valve B opens t o drain t he t ank.

4. When t he t ank level becom es low



Sw it ch B becom es ON



Valve B is closed

Wat er inj ect ion

processing

( St ep label A1)

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Operat ion Of St ep Sequence ( Exam ple)

Wat er inj ect ion

processing

( St ep label A1)

Wat er drain

processing

( St ep label A2)

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Num ber Of Condit ion & Act ion Signal

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Num ber Of Condit ion & Act ion Signal

Ta ble : Com bin a t ion of Con dit ion & Act ion Sign a l Cou n t s

N u m be r Of Con dit ion Sign a l

N u m be r Of Act ion Sign a l

8

56

16

48

24

40

32 ( default )

40

24

48

16

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Rule Ext ension

The num ber of rules in one sequence t able is fixed at 32 & cannot be m odified. However, if t he

num ber of rules in a sequence t able is not enough t o describe one phase unit , it can be ext ended in

t he 32- rule unit by connect ing t o anot her sequence t able. The num ber of rules can be ext ended for a

st ep- t ype sequence t able.

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Sw it ch I nst rum ent Block

Valve Monit oring Block ( VLVM)

Tim er Block ( TM)

Regulat ory Cont rol Blocks

Soft w are Count er Block ( CTS)

Calculat ion Blocks

Pulse Train I nput Count er Block ( CTP)

Faceplat e Blocks

Code I nput Block ( CI )

SFC Blocks

Code Out put Block ( CO)

Unit I nst rum ent Blocks

Relat ional Expression Block ( RL)

Resource Scheduler Block ( RS)

Logic Chart Block

Condit ion Signal Descript ion ( Funct ion Blocks and I / O Dat a)

Funct ion blocks t hat can be processed in a sequence t able are show n below .

I / O dat a t hat can be processed in a sequence t able are show n below .

Processing I / O ( Digit al I nput / Out put )

Soft w are I / O ( I nt ernal Sw it ch, Annunciat or, Global Sw it ch)

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The t able list s t he calculat ion

blocks t hat can be referenced

in t he condit ion signal as one-

shot oper at ion.

The form at is:

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The follow ing list s t he dat a

it em s of SFC block t hat can

describe dat a values in

condit ion specificat ions and

t heir set t ing ranges:

STEPN O: 1 t o 9 9

SW CR[ 5 ] : 0 t o 1 5

SW ST[ 5 ] : 0 ,1

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Creat e a logic sequence from t hese cont rol narrat ives:

Ca se 1

I n a cascade loop, if t he process variable of t he slave cont roller is

High-

High

alarm t hen t he slave cont roller m ode w ill have t o sw it ch t o

CASCADE

m ode and t he m ast er cont roller m ode w ill have t o sw it ch t o

AUTO

m ode.

How ever, t he operat or is allow ed t o change t he m ode of slave cont roller

t o

MANUAL

or

AUTO

m ode even t ough t he process variable is st ill in

High- High

alarm st at e.

Ca se 2

I n a cascade loop, if t he process variable of t he slave cont roller is

High-

High

alarm t hen t he slave cont roller m ode w ill have t o sw it ch t o

CASCADE

m ode and t he m ast er cont roller m ode w ill have t o sw it ch t o

AUTO

m ode.

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