SPT-PC RTU/IED SCADA Communication Gateway

SPT-PC RTU/IED SCADA Communication Gateway

ASE SPT-PC is a Windows PC-based communication gateway designed for use in SCADA environments to manage the flow of data and control operations between RTUs, IEDs, master stations, HMI systems, and user-developed application processes.


SPT-PC can manage master and remote device communication on Ethernet port(s) and up to 32 serial channels, integrate protocol translation and data concentrator capabilities, and provide external process access to telemetered data and controls through industry standard OPC, or enhanced proprietary, interfaces.  Support is available for a large number of serial and network protocols, including current technology protocols such as DNP 3 Serial, DNP 3 Wan/Lan, IEC 870-5-101, and IEC 870-5-104, as well as legacy “bit” protocols like Conitel 2020 and CDC I/II.

Support of both master/host and remote/slave operations are available for all protocols. Each communication port, serial or network, can be configured for a different protocol as well as for master or remote operations.

SPT-PC software replaces ASE’s previous PC based protocol translator, the RCOM product. The SPT-PC, which performs the same functions, has been redesigned for the latest in industry and coding standards. ASE can also provide I/O hardware for serial communications. While byte protocols can use a number of I/O cards including those manufactured by ASE, bit protocols require the ASE harware.

SPT-PC operates on configuration information entered through the program’s graphical user interface.  In addition to configuration capabilities, the GUI includes an online maintenance and diagnostic window for displaying:

  • A real-time view of all Master and Remote point data values
  • A visual indication of current communication status
  • Communication statistics, presented by channel and device
  • A low-level communication line monitor, for serial and network channels
  • Password-protected access to control output operations

SPT-PC modular design allows it to be configured to solve a variety of common SCADA communication requirements.


SPT-PC maintains independent communication on up to 32 serial communication lines and multiple Ethernet ports. Each line can be individually configured for protocol and master/remote communication. The Ethernet port can handle multiple connections and multiple protocols. Data obtained from any subset of remote devices can be routed to one or more SCADA masters. Where certain SCADA masters need, or are only allowed access to a portion of the points at a given Remote, an SPT-PC configuration can provide the required restricted mapping.

For selected protocols, SPT-PC supports listening mode operations. In this mode, SPT-PC eavesdrops on communication between a SCADA host and a set of remote devices. Point data values sent to the other host are copied into SPT-PC data storage, and made available for transmission to another host connected to SPT-PC.

The OPC server interface provides OPC XML-DA compliant HMI (Human Machine Interface) systems an access path to non-OPC compliant devices and to devices located remote from the HMI site. This capability extends to any protocol supported by SPT-PC’s protocol translator component. Information brought into SPT-PC’s common data area from any downstream protocol can be accessed through the OPC server interface. For many protocols, SPT-PC may provide the only OPC access path commercially available.

SPT-PC’s custom API provides added functionality required by a SCADA host when those requirements are not part of the OPC standards. Examples include access to extended point types, communication status and statistics, and on-line data base configuration.

The OPC client interface provides a data path between OPC XML-DA compliant devices and existing SCADA hosts without OPC capabilities. Data obtained from OPC devices are placed into the SPT-PC database and made available through the standard SCADA host communication path.

Operation Details

SPT-PC software completely manages the interface to all Remote units in their native protocols, including maintenance of all scan, control, and configuration requests. Information obtained from each Remote is processed for transmission to the host SCADA system, and commands received from the host are processed for transmission to the appropriate Remote. SPT-PC data acquisition software operates by continuously and independently issuing scans and other standard requests (e.g. time synchronization) to all remote devices defined in its database. Point information returned from the remote device is placed in a local data area. Scan requests received from the host are immediately processed and responded to, using this information. To ensure that the host is not presented with out-of-date information, communication status is maintained for each Remote. When the host requests information from a Remote that is not in a valid online state, no response to that request is transmitted, thereby propagating communication error conditions back to the host SCADA system. This approach provides fast response time to host data requests under normal conditions while protecting the integrity of system information under adverse conditions.
SPT-PC control software processes host issued Remote commands including digital, analog, and pulse output controls, and counter (pulse accumulator) freeze and freeze-with-reset requests. Negotiation of these commands is completed with the SCADA host, queued, and processed on a priority basis as corresponding communication lines become available. The list of Remote functions includes:

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  • Transmission of initialization commands required to bring a Remote on-line
  • Acquisition of analog data values
  • Acquisition of 1 and 2 bit digital input point values, including momentary change detect (MCD) bits
  • Acquisition of counter (pulse accumulator) data values
  • Acquisition of sequence of events data with time stamp
  • Forwarding control of digital output, analog output, and pulse output (raise/lower) point commands received from the host
  • Propagation of counter freeze and freeze-with-reset commands received from the host
  • Automatic, periodic, time synchronization of remote devices. Time is obtained either from a GPSS receiver or from a host time synchronization request. The synchronization of any Remote sets the SPT-PC/RPT internal high-precision clock which is then used as a time base to synchronize all target remote devices

SPT-PC operates as a process under the Windows 2000 , XP , 7, 8 and 10 operating systems. For most SPT-PC configurations, serial communication requires ASE-manufactured I/O boards, consisting of the PCI-bus BCOM8-56K. Designed by ASE specifically for remote device communication applications, this includes many features, some of which may not be available on other commercially available I/O boards.

SPT-PC software uses the watchdog timer as a tool to ensure system integrity by configuring it to reboot the computer in the event of a fatal hardware or software error. Since computer system boot-up procedures can automatically start the SPT-PC software, this feature provides an automatic system restart capability.

Communication Hardware

SPT-PC operates as a process under the Windows 2000, Windows XP, Windows Embedded, and Windows 7 operating systems. The SPT-PC can use any industry standard serial ports. Please contact ASE if you require specialty bit communications capabilities.

System Access and Configuration


The SPT-PC is configured with the SPT4-NET Configuration Editor, which is a graphical based tool for easy and convenient generation of configuration files used by the SPT Family of product. Point configuration information is specified through this Windows based utility program and downloaded through the SPT configuration and maintenance port, or through a network connection.

The configuration editor employs standard Windows procedures. An entire data base configuration can be entered and running within a few minutes. Changes to an active database can be downloaded and activated in seconds to minimize the entire configuration test and development process.
During on-line operation of the SPT-PC application, the configuration utility can be used to view diagnostic and program status information. This is a valuable diagnostic tool during initial installation and for on-going maintenance.

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