Open And Short Contact - FATEK FBS Series Manual

N times scan
X0
X1
A
Y0
Y0
Y0
Y1
Y1
Besides the TU/TD instructions which can detect the status change of reference operand, FBs-PLC also provides
the instructions to detect the change of node status (power flow). For details please refer the descriptions of FUN4
(DIFU) and FUN5 (DIFD) instructions at chapter 7.

4.2.2 OPEN and SHORT Contact

The status of OPEN and SHORT contact are fixed and can't be changed by any ladder instructions. Those two contacts
are mainly used in the places of the Ladder Diagram where fixed contact statuses are required, such as the place where
the input of an application instruction is used to select the mode. The sample program shown below gives an example of
configuring an Up/Down counter (UDCTR) to an Up counter by using the SHORT contact.
Ladder Diagram
X0
X1
Scan Time t
b c d e
a
A : The internal accumulator of PLC
7.UDCTR
X0
CV :
CK
PV :
U/D
X1
CLR
Y0
ORG
OUT
Y1
OUT
ORG
Y0
OUT
0
CUP
R
R 10
4 - 3
Mnemonic code
X 0 ---------------------
Y 0 ---------------------
Y 1 ---------------------
X 1 ---------------------
Y 0 ---------------------
N+1 times scan
a b c d
ORG X
LD SHORT
LD X
FUN 7
CV: R
PV: R
○
a
○
b
○
c
○
d
○
e
e
0
1
0
10