Technical data

8.2 Transmitting Multicast Messages by Direct Access
to Layer 2 Services
If the transmitted data are intended for several stations simultaneously
(using layer 2 services) you must use the following procedure:
➣
Program the same (local) SAP number (range 2..54) for each receiver
of the multicast message.
➣
Create the (request) header for the block of data to be transmitted, as
follows:
The station address 7F
H
is a global address for this application. Multicast to
all stations is only possible when the same (local) SAP is set up for every
L2 station and this SAP is entered as the DSAP/RSAP in the request
header of the sender. Fig. 8.12 illustrates which stations receive an SDN
frame with DSAP/RSAP 10 and address 7F
H
.
Byte
1
2
3
4
0
DSAP/RSAP=no. of the SAP programmed
5
6
7
for each receiver
...........
...........
...........
...........
...........
rem_add_station = 7F (global address)
H
service_code =01 (SDN)
H
Free Layer 2 Communication B8976060/02
Volume 1 8 - 28