SDT 5000 User Manual
Document MBUD-0109v11
6. RTU PORT
There are many Remote Terminal Units (RTU’s) in the market today, each with its own interfacing
requirements. The SDT 5000 was designed to interface to as many different RTU's as possible. This
chapter describes the details and features of the SDT 5000 RTU port interfacing capability.
The Remote Terminal Unit (RTU) port has several distinct modes of operation. The modes are
Transparent Protocol Mode, AT Mode, PPP Mode and Narrowband Protocol Mode. Each protocol
mode is described below.
The Transparent protocol mode is intended for use with existing RTU’s that either don’t have a
protocol or have a simple protocol already implemented. This mode is intended for ‘dumb’ RTU
devices, which send serial data and or expects to receive serial data. The intelligence for sending and
buffering the data is provided by the SDT 5000.
AT Mode provides standard phone modem emulation. This mode was loosely based on a USR
Modem. This mode is intended for devices, which are already programmed to support a standard
phone modem.
PPP Mode provides a standard PPP interface (RFC 1661) to the SDT 5000. PPP Mode is currently
under development and will be released TBD.
Narrowband Protocol (NBP) Mode is a proprietary protocol, which provides reliable communications
between the RTU and SDT 5000. NBP provides the RTU with full control over the data transfer to
and from the SDT 5000. NBP primitives provide access to X25, Command server, and IP packets.
6.1 Waking up or controlling an RTU
The SDT 5000 supports several means of awakening or notifying an RTU that has entered an idle or
low power state. These methods include:
1.
DSR, DCD control lines can be asserted when the CPU powers up, or when a connection is
established to the RTU port sub-address. The DSR and DCD operating modes are defined
based on the operating mode.
2.
Control of output switches via the command server.
3.
Sending a message to the RTU.
6.2 Supported
protocols
6.2.1 TRANSPARENT PROTOCOL MODE
Transparent protocol is a configurable mode that is intended to provide communications with a
host with no changes on the RTU.
Messages from the host to the RTU are unconstrained in length. Messages from the RTU to the
SDT 5000 may be up to 8 Kbytes long. Messages from the host to the RTU are not buffered and
are transmitted as they are received. If the flow control prevents the data from being sent to the
RTU the X25 data packets will not be acknowledged and the connection will timeout. The SDT
Version 1.1, 03/24/06
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