Siemens SIMATIC TIWAY 1 - Manual (Page 64)

CONFIGURING THE HOST COMPUTER PORT
UNILINK HOST ADAPTER 3–6
USER MANUAL
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
Modem Modem
Modem
Modem
UNILINK
Host Adapter
UNILINK
Host Adapter
UNILINK
Host Adapter
TIWAY1
Network #1
TIWAY1
Network #2
TIWAY1
Network #3
4-wire leased line
or equivalent wire
Figure 3–6 Multidrop Host Interface Circuit
NOTE
You should select half-duplex operation for the
modems when you multidrop to prevent the network
modems from simultaneously raising the carrier.