Advantech ADAM-6050 18-Channel Isolated Digital I/O Modbus TCP Module ADAM-6050-BE Scheda Tecnica

You can see the DO 0 will only be triggered when falling edge of DI 0 
occurs. In the example project we provide, the DO status will remain 
logic high for 1 second. Then it will back to logic low. When PLC is used 
for this kind of application, the ladder diagram will look similar to Figure 
7.35 below:

When you use GCL to achieve falling edge application, 3 logic rules, 1 
Internal Timer (Timer 0) and 1 Internal Flag (Flag 0) are needed. Please 
refer to Figure 7.36 below for GCL logic architecture. With logic rule 3, 
DO 0 value is controlled by DI 0 and Flag 0. Flag 0 value is logic False at 
beginning. 

When falling edge occurs (DI value changes from logic high to logic 
low), DO will be activated (logic rule 3 are satisfied), and Timer 0 starts 
to count time (logic rule 1 are satisfied). After Timer 0 counts up to the 
specific time interval (1 second), Flag 0 will become logic True by logic 
rule 2, making DO 0 value logic low (logic rule 3 are not satisfied). The 
GCL architecture is similar to the ladder diagram.

(     )

T0

[        ]

T0 ≧ 1

(     )

DI 0

(     )

Flag0

DO 0

DI 0

Flag0