Ladder Diagram Structure And Terminology - FATEK FBS Series Manual

1.3 Ladder Diagram Structure and Terminology

Element
Origin line Origin line
Network 1
Network 1
Network 2
Network 2
Network 3
Network 3
As shown above, the Ladder Diagram can be divided into many small cells. There are total 88 cells (8 rows X 11 columns)
for this example Ladder Diagram. One cell can accommodate one element. A completed Ladder Diagram can be formed by
connecting all the cells together according to the specific requirements. The terminologies related to Ladder Diagram are
illustrated below.
Contact
Contact is an element with open or short status. One kind of contact is called "Input contact"(reference number prefix with X)
and its status reference from the external signals (the input signal comes from the input terminal block). Another one is
called "Relay contact" and its status reflects the status of relay coil (please refer to
number and the contact status depends on the contact type. The contact elements provided by FB series PLC include: A
contact, B contact, up/down differential (TU/TD) contacts and Open/Short contacts. Please refer to
Relay
Same as the conventional relay, it consists of a Coil and a Contact as shown in the diagram below.
Node Parallel block
Element Node Parallel block
X1 X2
X0 X1 X2
X0
X7 X10
X7 X10
X10 X11 X11
X10
Y4
Y4
X12
X12
M1 M1 X14 X14 X20 X20
Y0 M6 M6
Y0
X16
X16
(Remark：The maximum size of FBs-PLC network is 16 rows×22 columns)
Relay coil
Sample Ladder Diagram
Serial block
Serial block
X3
X3 X4 X5 X5
X4
X9
X9
Branch
Branch
Y0
A
Y0
B
COIL
Y0
TU
Y0
Y0
TD
1 - 5
X6
X6
). The relation between the reference
for more details.
Relay contacts
Y0
Y0
Y2 Y2
/
Y4
Y4
Y5
Y5
/