Mitsubishi Electronics FX1S manual Moving Between STL Steps, Using SET to drive an STL coil

FX Series Programmable Controllers STL Programming 3

3.4Moving Between STL Steps

To activate an STL step the user must first drive the state coil. Setting the coil has already been identified as a way to start an STL program, i.e. drive an initial state. It was also noted that using an OUT statement to driving a state coil has a different meaning to the SET instruction. These difference will now be explained:

3.4.1Using SET to drive an STL coil

•SET is used to drive an STL state coil to make the step active. Once the current STL step activates a second following step, the source STL coil is reset. Hence, although SET is used to activate a state the resetting is automatic.

However, if an STL state is driven by a
series of standard ladder logic instructions,	X000 S040	S020
i .e . not a preceding STL state, then
standard programming rules apply.	S020	S030
In the example shown opposite S20 is not
reset even after S30 or S21 have been	SET	S021
driven. In addition, if S20 is turned OFF,
S30 will also stop operating . This is	RST	S022
because S20 has not been used as an STL
state. The first instruction involving the
status of S20 is a standard LoaD instruction and NOT an STL instruction.

Note: If a user wishes to forcibly reset an STL step, using the RST or ZRST (FNC 40) instructions would perform this task.

X000

ZRST S21 S28

•SET is used to drive an immediately following STL step which typically will have a larger STL state number than the current step.

•SET is used to drive STL states which occur within the enclosed STL program flow, i.e. SET is not used to activate a state which appears in an unconnected, second STL flow diagram.

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