I am working with an embeded board ,Now Looking for a standard modbus library to use that in the board.anybody is there to suggest me to getting such a standard library?
There is no such thing. MODBUS implementations are typically _highly_ target specific. You can depart from the specifications indicating timing and _general_ message format and behavior. You can find them online.
As a company we have developed our own libraries many years ago and use these as we are familiar with them. However there are now more standard Modbus libraries available, but you will have to customise these to fit your board and application.
For instance commercial versions are here micrium.com/.../modbus
Open source libraries are here http://freemodbus.berlios.de/ http://www.libmodbus.org/
Many others are list on wikipedia en.wikipedia.org/.../Modbus
Stuart