TIWAY I Overview
1-2 SIMATIC TIWAY I Series 500 NIM User Manual
1.1 TIWAY I System Overview
TIWAY I is an industrial Local Area Network designed to satisfy today’s
factory and plant requirements for data acquisition and control of
manufacturing processes. It is a significant enhancement of the Siemens
“Local Line,” which has supported the PM550 Programmable Controllers
and DS 990 computer products since 1980.
The TIWAY I network provides a reliable and flexible communication
architecture. Two communication media options are available:
•RS-232-C/423 — provides modem interface for large geographic
coverage.
•Local Line — provides high noise immunity for networks up to 25,000
feet (7620 meters).
Redundancy is supported for either choice of media. TIWAY I uses
High-level Data Link Control (HDLC) protocol with CRC-16 error-checking
and message-length error-checking, providing reliable network
communication.
Throughout this manual, the following networking terms are used.
•Primary — the HDLC network manager
•Secondary — the device operating as an HDLC secondary slave (NIMs,
UNILINK Secondary Adapters)
•Attached device — controller, robot, etc. (Siemens controller connected
to the NIM, robot connected to a UNILINK Secondary Adapter)