Mitsubishi Electronics FX1S manual Single Signal Step Control, Method 1 Using locking devices

FX Series Programmable Controllers STL Programming 3

3.5.2Single Signal Step Control

Transferring between active STL steps can be controlled by a single signal. There are two methods the user can program to achieve this result.

Method 1 - Using locking devices

FX1S FX1N FX2N FX2NC

In this example it is necessary to program separate locking devices, and the controlling signal must only pulse ON. This is to prevent the STL programs from running through.

The example shown below identifies the general program required for this method.

- S30 is activated when M0 is first pulsed ON.

-	The operation of M1 prevents the sequence	M0
	from continuing because although M0 is ON,
	the transfer requirements, need M0 to be ON	S 30	PLS	M1
	and M1 to be OFF.
- After one scan the pulsed M0 and the ‘lock’		M0
	device M1 are reset.	M1
-	On the next pulse of M0 the STL step will
	transfer program control from S31 to the next	S 31	PLS	M2
	step in a similar manner. This time using M2 as
	the ‘lock’ device because dual coils in	M0
	successive steps is not allowed.
- The reason for the use of the ‘lock’ devices M1		M2
	and M2 is because of the handshaking period
	when both states involved in the transfer of
	program control are ON for 1 program scan. Without the ‘locks’ it would be possible to
	immediately skip through all of the STL states in one go!

Method 2 - Special Single Pulse Flags

FX1S FX1N FX2N FX2NC

Using the pulse contacts (LDP, LDF, ANP, etc.) and a special range of M devices (M2800 to M3071) the same result as method 1 can be achieved. The special feature of these devices prevents run through of the states, as only the first occurrence of the LDP instruction will activate.

The example program below shows the necessary instructions.

- Assume S50 is already active.		X001
- When X01 activates M2800, this in turn			M2800	Do not use the
		LAD0		step control
	activates the LDP M2800 instruction in	M2800
				device in a
	S50 and the flow moves on to step	M2800
				pulse contact
	S51.
				within the main
-	The LDP M2800 instruction in the			program body.
	transition part of S51 does not execute
	because this is the second occurrence	S 50	M2800
	of M2800 in a pulse contact.	M2800		SET	S51
- When X01 next activates M2800, the		S 51	M2800	SET	Snn
	LDP instruction in S51 is the first	M2800
	occurrence because S50 is now
	inactive. Thus, control passes to the
	next step in the same manner.
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