kapil 
hello to all members, well first thing is i m new to embedded system programming so sorry in advance for any mistake.The problem that i m having is that i m using mini2440 ARM9 board with WinCE n trying serial communication using MODBUS protocol i've written code in vb .net 2005 using serial class provided with .net, after compile ther is communication between pc's hyper terminal and board but when i try to communicate with emulator like MODScan or any other then nothing is happening.i mean whether i try to query slave for either read or write ,coil or register (board as master) then there is no responce from either 1. i cant get what the problem or where the problem is whether H/W or S/W ?? thanks in advance Regards kapil