Mitsubishi Electric MELSEC iQ-R Series Programming Manual page 105

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 (including
stop and 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.
• Similarly, no step relay is assigned to any missing step No. within a block. The relevant bit is always 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 Nos. 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 b12 b11 b10 b9 b8 b7 b6 b5 b4 b3 b2 b1 b0
S15 to S0 0
S6 S5 S4 S2 S1 S0 S8 S7
Block2
b15 b14 b13 b12 b11 b10 b9 b8 b7 b6 b5 b4 b3 b2 b1 b0
S31 to S16 0 0 0 0 0
(3)
(1) Stored data
(2) Step numbers in a block
(3) All 0s for missing blocks
Any step No. can be assigned to each step (except end step).
• Assign step numbers 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 first initial step in a block.
Step numbers that can be assigned in a block range from 0 to 511. Any step No. exceeding the upper limit cannot be
assigned. Any step No. must be unique within a block. Same step numbers can be used between 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 Specifying the current target
other than SFC block
program
Specifying a block different
from the current target block
■ Precautions
• Even if "Output Mode at Block Stop" of the SFC setting is off, the step relay is on when the step is stopped the operation.
0 0
S5 S4 S2 S1 S0
Block0
0 0 0 0 0
S12 S11 S10 S9
Block2
Device
notation
S23
BL12\S23
S23
BL12\S23
(1)
(2)
(1)
S8 S7 (2)
Description
The block name can be omitted when specifying a step in the same block
Specify the target block No. and step No.
The block name can be omitted when specifying a step in the target block
Specify the target block No. and step No.
8 SFC PROGRAM
103
8.2 Structure
8