Technical data

Chapter 9 – Communications
Siemens Building Technologies, Inc. 77
Chapter 9 — SED2 Communications
Overview
The SED2 drives are a family of inverters that are built, sold, and serviced by Siemens Building
Technologies, Inc.- Adjustable Frequency Drives Group (SBT-Drives). Siemens Building
Technologies has a Protocol 1 (P1) communication driver, FLN connection, and point database
that is built into their drives and allows them to coexist on an APOGEE network with other floor
level network (FLN) devices.
The Siemens Building Technologies representative is responsible for proper configuration of the
drive for its primary application as well as field panel programming, to make use of the drive
functionality in the building automation system.
Chapter 9 describes how to access the SED2 from a field panel and how to use a SED2 as part
of a larger control scheme.
Using the Serial Interface
The serial interface uses an RS-485 two-wire connection. Up to 30 drives can connect on a single
RS-485 link, and drives can be addressed individually or with a broadcast message. This
configuration requires a separate master controller and the drives act as slaves.
Using a serial interface has several advantages:
• Wiring can be greatly reduced.
• Control functions can be changed without rewiring.
• Parameters can be set up and changed via the interface.
• Performance can be continuously monitored and controlled.
Working with Serial Communications
Introduction
This section describes the hardware aspects of the serial communications that are used with the
SED2. It does not discuss or detail the software protocols that are used or how to debug the
software. Software protocols are discussed later in this section.
RS-232 and RS-485 Serial Interfaces
Serial communications use carefully defined hardware and software protocols.
The software protocol defines the baud rate, word length, and meaning of the signal, and can be
defined by designers for their particular needs. Standards can also be specially developed, but
most users adopt an existing standard. Typical standards are RS-232 and RS-485. These
standards define voltages, impedance, etc. but not the software protocol.