Hi
There is a (commercial) MODBUS extension package to the uTasker project for Kinetis which runs 'out-of-the-box' on a K60 tower board:
http://www.utasker.com/modbus.html
It does master and/or slave ASCII/RTU and Modbus TCP and can be used as Modbus gateway or router. Multiple masters and slaves can be used on multiple UARTS and/or TCP sockets as well as via USB.
Detailed user's guide: http://www.utasker.com/docs/MODBUS/uTasker_MODBUS.PDF
Regards
Mark