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SoftPLC System Architecture Overview

What is SoftPLC®?

SoftPLC is the embedded software technology inside every SoftPLC controller CPU. SoftPLC literally turns an embedded computer into a high-performance, feature-rich Programmable Automation Controller (PAC), combining the functions of a proprietary PLC with the benefits of both an open architecture design and computers.

SoftPLC is suitable for applications ranging from remote RTU's, to individual machine control, to networked line/cell control, to complete plant-wide control systems. SoftPLC's have been used in virtually every industry in tens of thousands of applications throughout the world.

Key Features

• Reliable solution for both process and machine control
• Deterministic, high speed program execution
• “Unlimited” user logic and data table memory
• Ladder logic and data table addressing similar to Allen-Bradley PLC-5/SLC-500
• Fully documented applications, all documentation resides in the SoftPLC controller
• Supports I/O systems and other devices from hundreds of vendors
• Supports a wide variety of ethernet and industrial network and serial protocols
• Advanced network security functions
• Compatible with all HMI/SCADA products, including user generated PC based operator interfaces
• Embedded web server
• Supports user functions written in C++ or Java

Capacity Specifications

Specifications related to hardware (eg: number of ports, memory, etc.) vary by Controller model, the specifications listed here apply to most SoftPLC Controller models.

• ~100M rungs of ladder logic
• ~100M data table elements
• Over 16K digital I/O points plus unlimited analog (normally limited by I/O hardware, not SoftPLC)
• 16 different I/O or device drivers can be used simultaneously (hardware dependent)
• Supports up to 36 COM ports
• Supports up to 32 communication network channels

SoftPLC Overview

Gatecraft Linux

SoftPLC runs on Gatecraft(TM) Linux, which is an embedded Linux operating system distribution developed by SoftPLC Corporation. Using Linux provides benefits such as complete system logging of critical operations, open communication standards like SSH, FTP, PPP, SNMP, and more. However, most users require no knowledge of Linux to use SoftPLC, the operating system is transparent from users.

SoftPLC Controllers are embedded systems with no fragile components such as a hard drive, monitor or user input device. Also, unlike many control software products, SoftPLC doesn't put your system at risk by running on an office platform like Windows or Windows “band-aids”, there is no need to be concerned about “the blue screen of death” or other applications running in the computer causing the controller to become non-deterministic or to fail. SoftPLC Controllers are designed to run 365 days a year, 24 hours per day – and do!

Firewall

A feature of Gatecraft Linux is the built-in high-end firewall capability, which is included in each SoftPLC for no additional cost. Gatecraft Shield protects ethernet-to-ethernet connections and Gatecraft Junction protects PPP modem communication. Details on Gatecraft security functions, including Wireless Access Point (WAP) features can be found at the Gatecraft website.

Performance & Operation

SoftPLC runtime control software is the “firmware” in SoftPLC Controllers, and is a multi-tasking 32-bit “kernel”. When the computer boots up, SoftPLC loads and begins running the control application. SoftPLC has a synchronous scan cycle – it reads input data, executes the user logic program, and updates output data. Simultaneously, SoftPLC processes communication requests through multiple ports, and runs other processes such as the optional web server, user functions, and the firewall.

SoftPLC has 4 operating modes, which are controlled by TOPDOC or through an optional hardware keyswitch provided on some Controller models:

• Program/Remote Program – Communications are active, but logic and I/O scan are not
• Run/Remote Run – Normal operation
• Remote Test – Communications, logic and input scan are active, but output scan is not
• Fault – (Normally caused by user logic errors) Communications are active, but logic and I/O scan are not

Online run-mode program changes can be made, there is no “compile” process. There is no need to stop the machine/process to edit a program.

Throughput performance (scan time) is based on the specific Controller and I/O hardware, the number of optional processes running, as well as the application program instruction mix. In general, SoftPLC scan times are faster than traditional PLC's. If very fast performance is required, this can easily be achieved by proper hardware selection and application design.

Application Logic & Programming

SoftPLC Controllers are programmed, maintained and configured with TOPDOC® development software, which runs on Windows or Linux.

User Logic

SoftPLC's are programmed in industry standard ladder logic. Maintenance personnel are already trained and familiar with the programming and troubleshooting of ladder logic based control systems. This makes the transition from "hard" PLC's to SoftPLC much easier.

SoftPLC application programs can be huge! Ladder programs can contain up to 9,998 program files of up to 10,000 rungs each, arranged as a main program with subroutines.

Instruction Set

SoftPLC's basic ladder logic instructions are a superset of the Allen-Bradley PLC-5 and SLC-500. In fact, they are similar enough that an existing PLC-2/PLC, PLC-5, SLC-500, or PLC-3 program can be easily converted, then loaded into SoftPLC. Standard ladder instructions include:

• Contacts, Coils & Branching
• Timers/Counters
• Data Comparisons/Moves
• Math & Logical Operations
• Shift Registers/Sequencers
• Jumps, Subroutines, For/Next
• ASCII String Functions
• Specials (PID, Peer-to-Peer Messages, Diagnostics)

Loadable Functions

The SoftPLC instruction set is user extensible through the use of loadable functions called TLI's (TOPDOC Loadable Instructions). TLI's are created in C/C++ or Java language with the SoftPLC Programmer's Toolkit.

SoftPLC provides a number of free TLI's including:

• COMGENIUS - useful for general purpose ASCII or Modbus communications to/from RS-232, -422 or -485 devices through SoftPLC's COM ports
• SENDMAIL - allows SoftPLC to send email or text messages (including attachments) to devices such as computers, pagers, cell phones, etc.
• LOGDATA – instructions for event or time driven data acquisition
• DATABASE READ - Read data from a SQL database
• Instructions to work with other vendor's devices (eg: motion control, bus level I/O)
• Industry/application specific instructions to solve specific needs (eg: CONVEYOR instructions for part sorting/tracking applications)
• and others

TOPDOC dynamically learns about any TLI's from SoftPLC. These instructions are displayed on the screen just like other standard ladder logic instructions, complete with instruction and parameter names, customized by the instruction designer (not simply as "Custom Routine", "Parameter A", "Parameter B", etc.)

TLI's are even integrated into TOPDOC's editing menu system! TLI's you use appear in the pull-down menu system for program editing: both on-line or off-line.

Data Table

SoftPLC's data table can be configured with up to 9,997 files of 10,000 elements each (9997 files of 10,000 elements per file, plus 16K I/O tables and a SoftPLC Status file). The data table files can be independently user configured to store either inputs, outputs, binary (bit), integers, timers, counters, hexadecimal, floating point, PID, strings and more. A special status file contains controller information, fault codes, real-time clock, and more.

SoftPLC's data table addressing mimics that of the Allen-Bradley PLC-5/SLC-500 which means:

• Users familiar with A-B PLC's have little or no learning curve
• Operator Interface products (HMI/SCADA) can work with SoftPLC using the vendor's A-B drivers

Documentation

SoftPLC application files(APP's) include not only logic and data table but also all documentation. APP's reside in the SoftPLC, so there is never a problem of attaching to the SoftPLC for maintenance and not having the latest documentation, or having to separately maintain program and documentation files. APP documentation includes:

• Tagnames (20 character address short description)
• Descriptors (address long description)
• Rung Comments
• Program File Comments/Tags, Data Table File Comments/Tags, APP Comment
• Program Sections (hot links to specific rungs)

A-B Conversions

Automated conversions and import utilities for PLC, PLC-2, PLC-5, or SLC-500 programs and documentation into SoftPLC/TOPDOC format provide an easy upgrade path from existing Allen-Bradley systems to SoftPLC. The conversion utilities are normally 99.5% complete. In most cases the existing A-B I/O system, HMI/SCADA, and networks can remain in place virtually unchanged. SoftPLC Corporation can also provide conversion services for PLC-3, PLC-5/250, or SoftLogix5 programs. Details can be found on the A-B conversion page.

Internal Relational Database

SoftPLC is the only controller which offers this powerful and useful capability, which we call "Property Tables."

As an internal database, Property Tables allow crucial process data to be accessed in one or two high speed program scans, rather than having to wait for the data having to come from an external source (another computer or controller) which must send the data through a communications network. Property Tables open the door to a whole host of cost savings by minimizing the steps and hardware required to store and manage the data, as well as reducing integration time of moving the data from one location to another. Having the data in the SoftPLC can also eliminate the need for an IT department to manage the hardware and software for a separate database.

I/O Capabilities

SoftPLC connects to I/O systems and other devices through the use of loadable software I/O drivers. SoftPLC I/O drivers are Loadable Modules (or TLM's) and, like user-defined instructions, can be easily developed through the use of the optional SoftPLC Programmer's Toolkits.

SoftPLC Corporation has developed and supports drivers for the more popular I/O systems, and these drivers are included with SoftPLC Control Software at no charge. Other drivers have been developed by I/O vendors or other third parties and are available through them, with links provided from the SoftPLC website Knowledge Base. The possibilities are virtually endless! If you are interested in an I/O system not listed, please contact SoftPLC Corporation.

I/O drivers currently included with SoftPLC are listed in our Knowledge Base, along with detailed information on the hardware interfaces and use of the drivers. Some of the most popular drivers are:

• SoftPLC In Tealware™
• A Series Ethernet/Wireless I/O
• Allen-Bradley Remote I/O (1771), Block (1791), Flex (1794), SLC-500 remote I/O, and all compatible devices
• Profibus, DeviceNet
• ModbusTCP Ethernet

SoftPLC's maximum digital I/O capacity is 8192 Inputs plus 8192 Outputs. Additionally, drivers include support for analog, digital and special I/O. I/O forcing is independently controllable for inputs and outputs. Analog I/O is usually in addition to the digital maximum. What's more, you can load up to 16 different I/O drivers simultaneously, allowing a single SoftPLC system to utilize a mix of different vendor I/O systems.

For Allen-Bradley Remote I/O, Block Transfer is supported for special modules or other devices that can connect to the RIO link (e.g.: drives, operator interfaces). For some other I/O systems, custom ladder instructions (TLI's) are included for support of special modules (e.g.: multiplexer or positioning cards).

SoftPLC also supports an optional keyswitch driver, allowing your SoftPLC to support local operating mode control, in addition to the standard remote mode control from TOPDOC.

Motion Control

SoftPLC provides a number of options for motion control. Simple control can be accomplished via I/O modules, such as in Tealware. For more complex, multi-axis control, SoftPLC can interface to motion controllers from a wide variety of vendors using industry standard buses such a SERCOS, Profibus, DeviceNet, and others. Additionally, PC-based PCI or PC/104 motion cards can be installed in certain SoftPLC Processors and TLI's can be used to communicate tuning, scaling, trajectory, and velocity data over the backplane, using simple ladder logic commands. SoftPLC can then send data to each axis on an event-driven or timed basis.

Networking & Communication

Communication channels, limited only by hardware constraints, are available to SoftPLC in addition to the I/O channels. The communication channels can be selected in combinations of:

• COM Port (DF1 Protocols)
• A-B TCP/IP Ethernet
• ModbusTCP/UDP Ethernet
• Modbus Serial Master/Slave
• Data Highway Plus/Data Highway I

These channels can be thought of as being equivalent to the ports on the front of a traditional PLC. They provide access to SoftPLC's data table for application software programs that perform operator interface, data acquisition, etc. The channels are also used by TOPDOC to monitor, change, and upload/download the program logic and data table. Additionally, SoftPLC systems can communicate peer-to-peer to each other or to Allen-Bradley PLC's over these channel, via a messaging facility.

Multiple computer applications or other PLC's may be accessing SoftPLC from any one or combinations of these channels at the same time. Broad area or plant-wide solutions are easily implemented with SoftPLC's powerful networking capabilities - at much less cost and greater transmission rates than traditional PLC solutions.

Whats more, SoftPLC's include an embedded firewall for secure networking.

Operator Interface (HMI/SCADA)
Choose Your Favorite Operator Interface Products

Any software applications with PLC-5/SLC-500 data table access support can communicate with SoftPLC. This includes products such as Wonderware, Intellution, Indusoft, Maple Systems, Panelmate, Indusoft, Panelview, and many many others. You can also use OPC via server products that support the A-B PLC-5, such as Kepware or Matrikon. Applications developed in Visual Basic, Visual C++ or other languages that can access PLC-5 data tables using a driver toolkit, such as the ONE Toolkit and Drivers available from SoftPLC Corp are also an option. SoftPLC supports data table access commands which are a super-set of Allen-Bradley's Data Highway Plus command set. SoftPLC also provides operator interface products.

Web Server

SoftPLC's can include an optional embedded web server which allows a web browser to be used as an operator interface. Click here for details on the web server and included utilities. You can also connect to a SoftPLC web server demo system.

FTP/SSH Servers

SoftPLC includes an FTP and an SSH server which provide for easy remote maintenance of files in the SoftPLC CPU from other computer systems. Over any TCP/IP connection (including the internet), using any FTP/SSH client program, you can:

• View/edit SoftPLC configuration and log files
• Remotely start/stop the SoftPLC or Web Server
• Upload/download user application files, web pages, documentation
• Upload/download SoftPLC program files/drivers ("firmware" updates)
• Access the Gatecraft firewall configuration utility in SoftPLC
• and more!

Ordering Information

SoftPLC Control Software is available in 4 sizes, the only variation is in the number of digital I/O points the system can control. All sizes include support for an unlimited number of analog points. (Note that the total I/O points allowed will vary based on the I/O hardware you choose.)

• SPZ-LT Max. 128 In/128 Out
• SPZ-1K Max. 1024 In/1024 Out
• SPZ-2K Max. 2048 In/2048 Out
• SPZ-8K Max. 8192 In/8192 Out

For SoftPLC CPU's, you specify the runtime size as part of the catalog number, therefore, it is not purchased as a separate item. If you are building your own controller CPU, specify one of the above software products.