User manual

1 Publication 1760-UM001A-EN-P
Chapter 8
Inside Pico
Circuit Diagram Cycle
In conventional control systems, relay control processes all the circuit connections
in parallel. The speed with which a relay switches is thus dependent on the
components used, and ranges from 15 to 40 ms for relay pick-up and drop-out.
With Pico, the circuit diagram is processed with a microprocessor that simulates
the contacts and coils of the relay logic and thus processes all switching operations
considerably faster. Depending on its size, the Pico circuit diagram is processed
cyclically every 0.5 to 40 ms.
During this time, Pico passes through five segments in succession.
Figure 8.1 How Pico Evaluates the Circuit Diagram:
In the first three segments, Pico evaluates the contact fields in succession. As it does
so, Pico also checks whether contacts are connected in parallel or in series and
stores the switching states of all the contact fields.
In the fourth segment, Pico assigns the new switching states to all the coils in one
pass.
The fifth segment is outside the circuit diagram. Pico uses this to make contact
with the “outside world”: Output relays “Q1” to “Q6” are switched and inputs
“I1” to “I12” are read. Pico also copies all the new switching states to the status
image register.
Pico only uses this status image for one cycle. This ensures that each circuit
connection is evaluated with the same switching state for one cycle, even if the
input signals “I1” to “I12” change their status several times within a cycle.
T2--------{Q1
I2-I3-----RT2
123 45
1
2
3
4
I1-I4-
1-TT2
P1-
.. ...
I1-Q1----{Q8
Range
Circuit Connections