How to Use the Step Ladder Program Block
Appendix 1
215
How to program for step progression control
To execute specific processing in each process, program the step sequence as follows:
1) Execute the SET command at the end of STEP n as the input condition for moving to another step, and set
the internal switch. Program execution moves to next STEP n+1.
2) Execute the specific process at the start of next STEP n+1 taking the internal switch as the input
conditions. Reset the internal switch after completion of the specific process.
Example
The following shows an example where the PID value is switched at each process to
simultaneously stop and start pump operation.
Process 1
(step 01)
P1
I1
D1
Pump ON
Process 2
(step 02)
P2
I2
D2
Continuation of pump
ON
Process 3
(step 03)
P3
I3
D3
Pump OFF
Condition a
Condition b
Basic PID
Block Model
011
Constant ITEM
Setting Block
Model 171
Address 102
Constant ITEM
Setting Block
Model 171
Address 103
Constant ITEM
Setting Block
Model 171
Address 104
Step Ladder
Program Block
Model 301
P
I
D
•
Setting of P1, I1, D1
•
Setting of P2, I2, D2
•
Setting of P3, I3, D3
Pump
start/stop