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4 SFC PROGRAM CONFIGURATION
MELSEC-Q
4.4 Controlling SFC Programs by Instructions (SFC Control
Instructions)
SFC control instructions can be used to check a block or step operation status (active/inactive), or
to execute a forced START or END, etc.
Using the SFC control instructions with an SFC program created with SFC program symbols, the
SFC program can be usually controlled easily. (A program execution management SFC program
cannot be controlled by using SFC control instructions.)
The types and functions of the SFC control instructions will be explained.
CPU Module Type
Name Instruction Expression Function
Basic
model
QCPU
High
Performance
Model QCPU,
Process CPU,
Redundant
CPU
Universal
model
QCPU
a, &a, la,
b, &b, lb
Sn
1
Step operation status
check instruction 0
a, &a, la,
b, &b, lb
BLm/Sn
• Checks a specified step in a specified
block to determine if the step is active
or inactive.
a, &a, la,
b, &b, lb
TRn
1
Forced transition check
instruction
a, &a, la,
b, &b, lb
BLn\TRn
• Checks a specified step in a specified
block to determine if the transition
condition (by transition control
instruction) for that step was satisfied
forcibly or not.
Block operation status
check instruction
a, &a, la,
b, &b, lb
BLm
• Checks a specified block to determine
if it is active or inactive.
MOV(P) K4Sn
D
1
MOV(P) BLm\K4Sn
D
DMOV(P) K8Sn
D
1
DMOV(P) BLm\K8Sn
D
BMOV(P) K4Sn
D
Kn 1
Active steps batch
readout instruction
BMOV(P) BLm\K4Sn
D
Kn
• Active steps in a specified block are
read to a specified device as bit
information.
Block START
instruction
s BLm
• A specified block is forcibly started
(activated) independently and is
executed from an initial step.
Block END instruction r BLm
• A specified block is forcibly ended
(deactivated).
Block STOP instruction PAUSE BLm
• A specified block is temporarily
stopped.
Block restart instruction RSTART BLm
• The temporary stop status at a
specified block is canceled, with
operation resuming from the STOP
step.
s Sn
1
s BLm\Sn
• A specified block is forcibly started
(activated) independently and is
executed from a specified step.
r Sn
1
r BLm/Sn
• A specified step in a specified block is
forcibly ended (deactivated).
Step control instruction
SCHG
D
2
• The instruction execution step is
deactivated, and a specified step is
activated.
s TRn
1
s BLm\TRn
• A specified transition condition at a
specified block is forcibly satisfied.
r TRn
1
Transition control
instruction
r BLm\TRn
• The forced transition at a specified
transition condition in a specified
block is canceled.
Block switching
instruction
BRSET
S
• Blocks subject to the “*1” SFC control
instruction are designated.
: Usable, : Unusable
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