Mitsubishi Digital Electronics FX0S Manual

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FX Series Programmable Controllers STL Programming 3

3-3

Combined SFC Ladder representation

Sometimes STL pro

g

rams will be written in hard cop

y

as a combination of both flow dia

g

ram

and internal sub-pro

g

ram. (example shown below).

Identification of contact states

3.3 How To Start And End An STL Program

Before an

y

complex pro

g

rammin

g

can be undertaken the basics of how to start and more

importantl

y

how to finish an STL pro

g

ram need to be examined.

3.3.1 Embedded STL programs

An STL st

y

le pro

g

ram does not have to

entirel

y

replace a standard ladder lo

g

ic

pro

g

ram. In fact it mi

g

ht be ver

y

difficult to do

so. Instead small or even lar

g

e section of STL

pro

g

ram can be entered at an

y

point in a

pro

g

ram. Once the STL task has been

completed the pro

g

ram must

g

o back to

processin

g

standard pro

g

ram instructions until

the next STL pro

g

ram block. Therefore,

identif

y

in

g

the start and end of an STL

pro

g

ram is ver

y

important.

3.3.2 Activating new states

Once an STL step has been selected, how is it used and how is the pro

g

ram ‘driven’?

This is not so difficult, if it is considered that for an STL step to be active its associated state

coil must be ON. Hence, to start an STL sequence all that has to be done is to drive the

relevant state ON.

There are man

y

different methods to drive a

state, for example the initial state coils could

be pulsed, SET or

j

ust included in an OUT

instruction. However, within Mitsubishi’s STL

pro

g

rammin

g

lan

g

ua

g

e an STL coil which is

SET has a different meanin

g

than one that is

included in an OUT instruction.

M8002

X0

X1

S 0

S 26

X0

X1

X15

S 22

S 27

K20

K20

T0

T7

Y22

T0

Y27

T7

Y20

Y26

• Please note the followin

g

convention

is used:

Normall

y

Open contact

Normall

y

Closed contact

Common alternatives are ‘a’ and ‘b’

identifiers for Normall

y

Open,

Normall

y

Closed states or often a line

drawn over the top of the Normall

y

Closed contact name is used, e.

g

.

X000.

LD

OUT

LD

SET

STL

OUT

LDI

OUT

RET

LD

OUT

RST

X000

Y004

X002

S009

S009

Y010

X003

Y006

X005

Y007

M080

Normal Ladder Program

Embedded STL Program

STL

S 22

SET S 27

T0

Y22

T0

K20

STL

S 27

Note: For normal STL operation it is recommended that the states are selected usin

g

the

SET instruction. To activate an STL step its state coil is SET ON.