Experienced SIXNET driver implementers will be pleased to know that the following simplifications have been implemented for this application:
The message length has been extended from one to two bytes. Since the only legal values of the first byte are zero and one and since no previous message could have such a short length, the first length byte identifies the new simplified format and indicates that the other simplifications listed below are in use.
Since the message length is now more than one byte, it is possible for message lengths to exceed 255 characters. In practice, we have not extended the amount of data permitted in a message for many reasons. What this does though is allow for the few extra bytes associated with the new two byte fields and guarantees that if messages grow (slightly) due to these few extra bytes, that no curtailment in the amount of data sent in any Universal driver message will occur.
The destination and source station address fields are permanently increased to two bytes to allow for full range station addressing in a simple format.
All three message formats (binary, hex and Ethernet fixed CRC). It is suggested that all three formats be supported by the slave to be tolerant of communication media limitations.