Latched (Battery Backed) Type State Relays; Role Of The Ret Instruction; Preliminary Knowledge For Creating Sfc Program - Mitsubishi Electric FX3G SERIES Programming Manual

FX /FX /FX Series Programmable Controllers
3G 3U 3UC
Programming Manual - Basic & Applied Instruction Edition
35.1.5

Latched (battery backed) type state relays

In the latched (battery backed) type state relays, the ON/OFF status is backed up by the battery or EEPROM memory
against power failure.
Use this type of state relay if the operation should be restarted from the last point before power failure.
35.1.6

Role of the RET instruction

• Use the RET instruction at the end of an SFC program.
When inputting an SFC program using GX Developer, however, it is not necessary to input the RET instruction
(because RET instruction is automatically written).
• In a PLC, two or more SFC blocks can be put between step 0 and the END instruction.
When there are ladder blocks and SFC blocks, put a RET instruction at the end of each SFC program.
35.1.7

Preliminary knowledge for creating SFC program

List of sequence instructions available in states
State relay
Initial/general state relay
Branch/recombination
state relay
• STL instruction cannot be used in interrupt programs and subroutine programs.
• When using SFC programs (STL instruction), do not drive state relays S using SET or OUT instructions in an
interrupt program.
• It is not prohibited to use jump instructions in state relays. However, it is not recommended to use jump instructions
because complicated movements will result.
*1. The MPS instruction cannot be used immediately after a state relay (STL instruction), even in a drive
processing circuit.
Special auxiliary relays
For efficiently creating SFC programs, it is necessary to use some special auxiliary relays. The table below shows
major ones.
Device
Name
number
M8000 RUN monitor
M8002 Initial pulse
STL transfer
M8040
disable
*1
STL state ON
M8046
Enable STL
*1
M8047
monitoring
*1. Processed when the END instruction is executed.
LD/LDI/LDP/LDF,
AND/ANI/ANDP/ANDF,
OR/ORI/ORP/ORF,
INV,MEP/MEF,OUT,
SET/RST,PLS/PLF
Drive processing
Transfer processing
This relay is normally ON while the PLC is in the RUN mode.
Use this relay as the program input condition requiring the normally driven status or for indicating the PLC
operation status.
This relay turns ON and remains ON only momentarily when the PLC mode is changed from STOP to
RUN.
Use this relay for the initial setting of a program or for setting the initial state relay.
When this relay is set to ON, transfer to the ON status is disabled among all state relays.
Because programs in state relays are operating even in the transfer disabled status, output coils do not
turn OFF automatically.
This relay automatically turns ON when any of state the relays S0 to S899 or S1000 to S4095 turn ON.
Use this relay to prevent simultaneous startup of another flow or as a process ON/OFF flag.
When this relay is driven, the device number of a state relay in the ON status having the smallest device
number among S0 to S899 and S1000 to S4095 is stored to D8040, and the state relay number in the ON
status having the next smallest device number is stored to D8041. In this way, up to eight state relays in
the ON status are stored in registers up to D8047.
• In the FX-PCS/WIN(-E), FX-30P, FX-20P(-E), and FX-10P(-E), when this relay is driven, the state
relays in the ON status are automatically read and displayed.
For details, refer to the appropriate peripheral equipment manual.
• In the SFC monitor in GX Developer, the automatic scroll monitoring function is valid even if this relay is
not driven.
Instruction
ANB/ORB/MPS/MRD/
MPP
Available
Available
Available
Available
Available Not available
Function and application
35 SFC Program and Step Ladder
35.1 SFC Program
MC/MCR
*1
Not available
*1
Not available
Not available
761
31
32
33
34
35
36
37
38
A
B