Siemens SIMATIC TIWAY 1 User Manual page 64

CONFIGURING THE HOST COMPUTER PORT
3.2.3 Multidrop Host Interface Circuit
You can multidrop up to 32 adapters using modems in a multipoint circuit as
shown in Figure 3–6. This allows the host computer to control multiple TIWAY I
networks; however, each adapter must use the BDLC protocol. Each adapter
must be assigned a unique address with dipswitches. The BDLC protocol uses
the addresses to route messages to the correct network. A multipoint circuit
represents the network layer of the Open Systems Interconnection model
described further in Reference 4 in the Preface and in the TIWAY I Systems
Manual (PPX:TIWAY–8101).
Host
Computer
UNILINK HOST ADAPTER
USER MANUAL
Modem
4-wire leased line
or equivalent wire
Figure 3–6 Multidrop Host Interface Circuit
You should select half-duplex operation for the
modems when you multidrop to prevent the network
modems from simultaneously raising the carrier.
UNILINK
Host Adapter
Modem
UNILINK
Host Adapter
Modem
UNILINK
Modem
Host Adapter
NOTE
3–6
TIWAY1
Network #1
TIWAY1
Network #2
TIWAY1
Network #3