User Guide

FS-8700-31 Siemens TIWAY I Page 1 of 23
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1. Siemens TIWAY I Driver Description
The Siemens TIWAY I driver allows the FieldServer to transfer data to and from devices
over RS-
232C using TIWAY BDLC “Host Adapter Command” protocol. The FieldServer can
emulate either a Server or Client.
Max Nodes Supported
FieldServer Mode Nodes Comments
Client 1 Only 1 client node allowed
Server 254 Up to 254 secondary PLCs
The FieldServer Siemens TIWAY I driver, hereafter simply referred to as the TIWAY driver,
can be used to emulate the host side of a Siemens Unilink Host Adaptor (UHA) using BDLC
“Host Command Protocol”. The original Siemens UHA device was used to interface other
host devices to a TIWAY I network as shown below:
The original Siemens UHA is really a protocol bridge in itself. It speaks “Host Command
Protocol” on the host interface which may contain embedded TIWAY primitives (commands)
and speaks Siemens TIWAY I protocol on its secondary interface. The FieldServer TIWAY I
driver emulates the UHA’s host interface when used in the server mode, however the
FieldServer does not speak Siemens TIWAY protocol and therefore cannot be used to
connect to legacy TIWAY devices directly. The driver’s use is primarily as a server to allow
legacy SCADA systems speaking “Host Command Protocol” containing TIWAY primitives to
communicate with modern PLCs speaking Modbus or other industrial protocols. The
accompanying FieldServer client driver in a configuration setup will typically be Modbus or
some other industrial protocol. The TIWAY driver’s use as a client is limited to emulating a
host to a UHA or for testing purposes.
The TIWAY driver operates in the Master Host Interface Unit ( MHIU ) mode and only
supports a limited selected set of Host Adapter commands and TIWAY primitives which are