Hi,

Kontroller

So my question is, is the ISO TCP connection processed only once during a PLC cycle? The only explination I could come up with is that the TCP data is processed independently from the PLC process cycle and the data is received and processed when i>=1.

Mike

open user communication is performed asynchronous! So depending on the cylce time of your CPU and amount of data to be send/received, the communication process (each call) may take several cpu cycles!

Difference between synchronous and asynchronous instructions

TRCV: Receive data via communication connection

Note

Because "TRCV" is executed asynchronously, the data in the receive area is only consistent when the NDR parameter is set to the value "1".

regards

sancruz

Hello,

Kontroller

Hi,

I have sometimes an issues with processing incomming ISO TCP data, where the T_RCV function is called in a FOR loop. Here is a simplified version of the code:

for i=1 to 5 do
call T_RCV;
variable_x := T_RCV_Data;
array_y[i]; := variable_x;
end_for;

What is happening is that sometimes I receive data but it is not written to the first array index ( where i=1). However, when I record a trace I can see data in variable_x.

So my question is, is the ISO TCP connection processed only once during a PLC cycle? The only explination I could come up with is that the TCP data is processed independently from the PLC process cycle and the data is received and processed when i>=1.

Mike

pls don't use any comm blocks execution inside any type of loop gold advice...