Mitsubishi Electric MELSEC iQ-F Series Programming Manual page 85

Assigning the step relay (S) areas to steps
The step relay is a device corresponding to each step in the SFC program. It is on when the relevant step is active (even in
the stop or hold state) and is off when the relevant step is inactive.
Step relays are assigned as follows.
• Step relays are assigned sequentially in order of block No. starting from block 0 in an SFC program and in order of step No.
within a block.
• No step relay is assigned to any non-existing block No.
• Step relays are assigned to missing step Nos. in one block. The bits of the missing numbers are constantly off.
• All bits after the step relays assigned in the last block are off.
Ex.
The following example shows the step relay assignments of the following block configuration.
• Block0: The largest step No. is 8, and step No. 3 and 6 are missing.
• Block1: Missing
• Block2: The largest step No. is 12, and step No. 3 is missing.
• Block3 and after: Missing
b15 b14 b13
S15 to S0
S6 S5 S4
Block2
b15 b14 b13
S31 to S16 0 0 0
Any step No. can be assigned to each step (except end step).
• Assign step Nos. in ascending order wherever possible because any missing step No. will decrease the
maximum number of steps that can be created.
• The step No. other than step No. 0 (S0) cannot be used for the initial step of the top line and left end.
Step No. 0 is assigned to the initial step in a block.
For the step Nos. that can be used per block, refer to the following.
Page 73 Specifications
Any step No. exceeding the upper limit cannot be assigned. Any step No. must be unique within a block. Same step Nos. can
be used in different blocks.
To specify a step relay in another block, use the following format.
Ex.
Specifying step No. 23 in block No. 12
Program type
SFC program In the same block
Other than block 12
Sequence program other Specifying the current target block
than SFC program
Specifying a block different from the current
target block
b12 b11 b10 b9 b8 b7 b6
0 0
- S2 S1 S0 S8 S7 -
b12 b11 b10 b9 b8 b7 b6
0 0 0 0 0 0 0
S12
(3)
b5 b4 b3 b2 b1 b0
0
S5 S4 - S2 S1 S0
Block0
b5 b4 b3 b2 b1 b0
S11 S10 S9 S8 S7
Block2
Device notation Description
S23 The block name can be omitted when specifying a step in the
same block.
BL12\S23 Specify the target block No. and step No.
S23 The block name can be omitted when specifying a step in the
target block.
BL12\S23 Specify the target block No. and step No.
(1) Stored data
(2) Step Nos. in a block
(3) All 0s for missing blocks
(1)
(2)
(1)
(2)
8 SFC PROGRAM
8.2 Structure
8
83