Creation Of Step Ladder Program (Sfc Program → Stl Program) - Mitsubishi Electric MELSEC FX3U Programming Manual

FX /FX /FX Series Programmable Controllers
3G 3U 3UC
Programming Manual - Basic & Applied Instruction Edition
35.2.4 Creation of step ladder program (SFC program → STL program)
The figure on the left shows one state relay extracted as an example from an SFC program.
Each state relay has three functions, driving a load, specifying a transfer destination and specifying a transfer
condition.
The step ladder shown on the right expresses this SFC program as a relay sequence.
In this program, a load is driven, and then the ON status is transferred.
In a state relay without any load, the drive processing is not required.
For the program creation procedure, refer to the description on SFC programs.
<SFC program>
20
STL
1
SET
21
<List program>
0 STL
1 OUT
2 LD
3 OR
4 OUT
5 LD
6 ANI
7 SET
*1. SET and RST instructions for a state relay are two-step instructions.
• When every state relay used in an SFC program is defined, programming is complete.
• Program a step ladder program starting from the initial state relay in the order of state relay ON status
transfer.
Make sure to put the RET instruction at the end of a step ladder program.
836
→ For the program creation procedure, refer to Subsection 35.1.3.
→ For the handling and role of initial state relays, refer to Subsection 35.1.4.
→ For latched (battery backed) type state relays, refer to Subsection 35.1.5.
Y010
X010
Y011
X011
X000 X001
TRAN
S20
Y010
The above program can be expressed in the list format
X010
(list program) shown on the left.
X011
The segment from the STL instruction to the RET
Y011
instruction is handled as a step ladder program.
X000
X001
*1
S21
35 SFC Program and Step Ladder
→ For RET instruction, refer to Subsection 35.1.6.
<Step ladder>
STL
Y010
X010
Y011
X011
X000 X001
SET
35.2 Step Ladder
S20
S21