
APPENDIX
Serial Bus Protocol
134
2.10
•
19.01.2007
5.3.3.4 Ethernet
Interworking
Hoeft & Wessel’s standard firmware provides ethernet frame transfer capabilities and
includes the necessary interworking.
Every module is delivered with its own ethernet MAC address, so that it can be directly
addressed from the network.
Every device attached to the radio module requires its own MAC address.
Every FT maintains a dynamic list of MAC addresses of all currently associated PTs.
Every PT manages a dynamic list of ethernet MAC addresses which it is able to reach.
The interworking allows for packet transfer between two devices being connected to different
PTs. Transfer is realised with the help of the FT serving as a relay station. From the received
packet’s address the FT firmware derives the information that the packet has to be resent
over the air again to reach its destination.
5.3.4 Implementation
The following characteristics must be considered for an implementation of the serial bus
protocol.
5.3.4.1 Addressing
Connected devices must have an address which is similar to ethernet MAC addresses.
A MAC address consists of 6 bytes (48 bits) in the representation B0:B1:B2:B3:B4:B5 (in the
order of transmission). B0 to B2 respresent the vendor ID. The LSB of B0 identifies if a
packet is a unicast (0) or multicast (1). So the vendor ID comprises 23 bit.
B3 to B5 is an unique number in the responsibility of the manufacturer.
The MAC address FF:FF:FF:FF:FF:FF indicates an ethernet broadcast.
As long as the system is not really connected to an ethernet the addresses may in principle
be arbitrary if they keep to the basic MAC address structure. The vendor ID 00:00:00 is not
assigned as a vendor ID and may therefore be used to generate pseudo MAC addresses for
the serial bus protocol, i.e. addresses like 00:00:00:B3:B4:B5 may be used.
In case the system is attached to a real ethernet network the MAC addresses used must be
worldwide unique, that means the manufacturer has to purchase his own vendor ID from
IEEE.
Hoeft & Wessel currently uses the vendor ID 00:30:2E. If the available numbering range is
exhausted a new Id will be applied.