A method and system is provided that enables generation of messages for various types of card activated terminal devices such as automated teller machines. Automated teller machines operate responsive to a variety of ATM message formats. The transaction processing system may generate ATM messages one of the ATM message formats using information associated with the ATM message format that is stored in a data store. The transaction processing system may include among its software components a message gateway router (MGR) which is operate to use information stored in the data store to convert messages from an internal message format to a variety of external message formats used by the automated teller machine.