Thankyou Eros,
I am sure that my communication port is COMM1.
About the ERR code seem no effect, the value always 0. I check with opening program in the same time with accesing comm1, the thin basic return ERR number still 0.
Would you like give me the sample of program?
The spec of program only read data (count = xxx + lfcr) that I send from my device, no need command request.
thank you verymuch

regard

hendryawan