I am using DB9 to DB15 serial cable inorder to reader one byte character send from the circuit I have designed, but I cannot read from the serial port why?

Are you sure your cable is wired correctly? Try plugging a null-modem adapter into one end or the other.

yes it is wired correctly, I tried it on my freinds computer using DB9 to DB9 serial cable,but when i used BD9 to DB15 I couldn't get a signal

To validate your wiring, do you have an adpater to convert your cable back to DB9 on the DB15 side to ensure data can flow through?

no I don't have,but can i change the wiring in the DB9 adapter so that data could be transmitted through the DB15 adapter?If yes please let me know how I must wire the DB9 adapter