Technical data

Another way of sending multicast messages to all stations is to use the

default SAP. This SAP which can be programmed with the Init editor of the

COM 5430 TF software package has the following function:

All receive messages with DSAP/RSAP information are automatically

assigned to the default SAP by the layer 2 firmware. To reach all stations

on the bus you must simply follow the procedure below:

➣

Assign a default SAP (range: 2..54) to each station

➣

Assign byte 2 (service_code) the value 01

(service: SDN)

➣

Make sure that the sender generates a frame without DSAP/RSAP

information. To do this, enter the value FF

in byte 5 of the request

header (DSAP/RSAP)

and

➣

Enter the value 7F

(global address) in byte 6 (rem_add_station) of the

request header

Station 2 Station 5 Station 3 Station 4 Station 1

SAP 12

SAP 10 SAP 10

SAP 10

SDN frame with DSAP/RSAP 10 and address 7F

Fig. 8.12 Sending Multicast Messages with the SDN Service

B8976060/02 Free Layer 2 Communication

8 - 29 Volume 1