
APPENDIX
Serial Bus Protocol
132
2.10
•
19.01.2007
5.3
Serial Bus Protocol
5.3.1 Introduction
For using the Data-Unwired DECT / FHSS modules in a point-to-multipoint system structure
the CLDPS protocol was implemented, which is based on the transmission of ethernet
frames. In case the modules shall neither be used in TCPIP nor SWAP mode, it is possbile
to redirect ethernet traffic directly to the RS-232 interface. In this case, a so called serial bus
protocol is used. As this is a lower layer protocol the application that integrates the module
must implement higher layer protocols. The serial bus protocol is explained in this sectiom.
5.3.2 Architecture
A serial bus system comprises a FT - bus master – and up to 64 PTs – bus ports. The
communcation is based on datagrams which are exchanged serially between FT and PTs.
The bus system accepts occasional losses of datagrams and implements its own re-transmit
procedures.
The radio system is based in a cellular structure. A radio cell comprises one FT and several
PT. To take part on a radio cell a PT must be attached to the FT. One FT may handle up to
64 PTs being registered simultaneously.
Systems comprising multiple radio cells allow for the PTs to change between cells (roaming).
A PT may only be registered to one cell at a time and will have to cancel its current
registration before registering to another cell’s FT.
CLDPS defines the radio protocol inside a radio cell, namely the MAC and DLC layer of the
OSI layer model (in the following refered to as clMAC and clDL). The bus protocol (NWK
layer, OSI layer 3) is not part of CLDPS.
Insofar CLDPS only supports data transfers between FT und PTs and vice versa. There is
no direct communication between two PTs.
The basic protocol architecture is shown here:
Bus
Bus
Radio
local
ETH Port
ETH Interworking
Interface Driver
PT
local
ETH Port
ETH Interworking
Interface Driver
FT
CLDPS DLC
(clDL)
CLDPS MAC
(clMAC)
CLDPS DLC
(clDL)
CLDPS MAC
(clMAC)
Interface Driver
Bus aster
Interface Driver
Bus Port
Figure 16: Protocol architecture