Current Flow; Contact, Nc Contact - Eaton ELC-PB Programming Manual

Scan time exception
The ELC can process certain items faster than the scan time. Program interrupts halt the scan
time to process the interrupt subroutine program. A direct I/O refresh instruction REF allows the
ELC to access I/O immediately during user program evaluation instead of waiting until the next
scan cycle.
1.2

Current Flow

Ladder logic follows a left to right principle. In the example below, the current flows through paths
started from either X0 or X3.
X1 X2
X0
X4
X3
Reverse Current
When a current flows from right to left, which makes a reverse current logic, an error will be
detected when compiling the program. The example below shows the reverse current flow.
X1 X2
X0
X4 X5
X3
a
b
X6
1.3 NO Contact, NC Contact
NO contact
Normally Open Contact, A contact
NC Contact
Normally Closed Contact, B contact
M N 0 5 0 0 3 0 0 3 E F o r m o r e i n f o r m a t i o n v i s i t : w w w. e a t o n . c o m
Y0
Y0
Y0
Y0
1 . E L C C o n c e p ts
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