User manual

Publication 1760-UM001A-EN-P
8-2 Inside Pico
How Does This Affect Creation of the Circuit Diagram?
Pico evaluates the circuit diagram in these five segments in order. You should
therefore remember two points when you create your circuit diagrams:
• The changeover of a relay coil does not change the switching state of an
associated contact until the next cycle starts.
• Always wire forward or from top to bottom. Never work backward.
Example: Switching One Cycle Later
This is the circuit diagram of a self-latching circuit. If I1
and I2 are closed, the switching state of relay coil {Q1 is
“held” via contact Q1.
1st cycle:
1st cycle:1st cycle:
1st cycle: I1 and I2 are switched on. Relay {Q1 picks
up.
Relay contact Q1 remains off since Pico evaluates from
left to right.
2nd cycle:
2nd cycle:2nd cycle:
2nd cycle: The self-latching function now becomes active. Pico has transferred the
coil states to contact Q1 at the end of the first cycle.
Example: Do Not Wire Backward
This example is shown in Creating and Modifying
Connections on page 4-8. It was used to illustrate how
NOT to program.
When wiring more than three contacts in series, use one
of the marker relays.
I1-I2-------{Q1
Q1
Circuit Diagram:
Start Condition:
I1, I2 switched on
Q1 switched off
I1-Q4-I3
------
I2-I4-{Q2
I1-Q4-I3-{M1
I2-I4-M1-{Q2