Filter
Top Products
FX Series Programmable Controllers Devices in Detail 4
4-8
4.4.3 STL Step Relays
States (S) are very important devices when
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 ➀
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.
Assigned states:
• 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
Monitoring STL programs:
• To monitor the dynamic-active states within an STL program, special auxiliary relay
M8047 must be driven ON.
STL/SFC programming:
• For more information on STL/SFC style programming, please see chapter 3.
IST instruction:
• For more information on the IST instruction please see page 5-67.
S2
X0
X1
X2
X3
1
S20
S21
S22
Y0
Y1
Y2