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FX Series Programmable Controllers

4-8

S t a t e s   ( S )   a r e   v e r y   i m p o r t a n t   d e v i c e s   w h e n
programming step by step process control. They are
used in combination with the basic instruction STL.
When all STL style programming is used certain states
have a pre-defined operation. The step identified as 

in the figure opposite is called an ‘initial state’. All other
state steps are then used to build up the full STL
function plan. It should be remembered that even
though remaining state steps are used in an STL
format, they still retain their general or latched
operation status. The range of available devices is as
specified in the information point of the previous
section.

•

When the applied instruction IST (Initial STate function 60) is used, the following state 
devices are automatically assigned operations which cannot be changed directly by a 
users program:

S0

: Manual operation initial state

S1

: Zero return initial state

S2

: Automatic operation initial state

S10 to S19

: Allocated for the creation of the zero return program sequence

•

To monitor the dynamic-active states within an STL program, special auxiliary relay 
M8047 must be driven ON.

•

For more information on STL/SFC style programming, please see chapter 3.

•

For more information on the IST instruction please see page 5-67.

S2

X0

X1

X2

X3

1

S20

S21

S22

Y0

Y1

Y2