Mitsubishi Electronics FX1S manual How To Start And End An STL Program, Embedded STL programs

FX Series Programmable Controllers STL Programming 3

Combined SFC Ladder representation

Sometimes STL programs will be written in hard copy as a combination of both flow diagram and internal sub-program. (example shown below).

Identification of contact states

•Please note the following convention is used:

￿Normally Open contact

￿Normally Closed contact

Common alternatives are ‘a’ and ‘b’ i d e n t i f i e r s f o r N o r m a l ly O p e n , Normally Closed states or often a line drawn over the top of the Normally Closed contact name is used, e.g. X000.

M8002

S 0

X0

X1

S 22

T0

S 27

T7

Y20

X0

X1

Y22 S 26

T0

K20

X15

Y27

T7

K20

Y26

3.3How To Start And End An STL Program

Before any complex programming can be undertaken the basics of how to start and more importantly how to finish an STL program need to be examined.

3.3.1Embedded STL programs

An STL style program does not have to entirely replace a standard ladder logic program. In fact it might be very difficult to do so. Instead small or even large section of STL program can be entered at any point in a program . Once the STL task has been completed the program must go back to processing standard program instructions until the next STL program block. Therefore, identifying the start and end of an STL program is very important.

3.3.2Activating new states

LD X000

OUT Y004

LD X002

SET S009

STL S009

OUT Y010

LDI X003

OUT Y006 RET

LD X005

OUT Y007

RST M080

Normal Ladder Program

Embedded STL Program

Once an STL step has been selected, how is it used and how is the program ‘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 many different methods to drive a state, for example the initial state coils could be pulsed, SET or just included in an OUT instruction. However, within Mitsubishi’s STL programming language an STL coil which is SET has a different meaning than one that is included in an OUT instruction.

STL	Y22
S 22
	K20
	T0
T0
SET	S 27
STL
S 27

Note: For normal STL operation it is recommended that the states are selected using the SET instruction. To activate an STL step its state coil is SET ON.

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