The Beckhoff TwinCAT software system turns any compatible PC into a
real-time controller with a multi-PLC system, NC axis control, programming
environment and operating station. TwinCAT replaces conventional PLC and
NC/CNC controllers as well as operating devices with:
- open, compatible PC hardware
- embedded IEC 61131-3 software PLC, software NC and software CNC
in Windows NT/2000/XP, NT/XP Embedded, CE.
- programming and run-time systems optionally together on one PC or
separated connection to all common fieldbuses
- PC interfaces are supported data communication with user interfaces
and other programs by means of open Microsoft standards (OPC, OCX,
DLL etc.)
TwinCAT architecture
The TwinCAT system consists of run-time systems that execute control
programs in real-time and the development environments for programming,
diagnostics and configuration. Any Windows programs, for instance visualisation
programs or Office programs, can access TwinCAT data via Microsoft interfaces,
or can execute commands.
A practically oriented software solution
TwinCAT offers a precise time-base in which programs are executed with
the highest deterministic features, independently of other processor
tasks. The real-time load on a PC is set with TwinCAT; defined operating
behaviour is achieved in this way. TwinCAT indicates the system load
for programs that are running. A load threshold can be set, in order
to assure a defined computing capacity for the operating programs and
for Windows NT/2000/XP. If this threshold is exceeded, a system message
is generated.
TwinCAT supports system diagnosis
The general use of hardware and software from the open PC world requires
some checking: Unsuitable components can upset the PC system. Beckhoff
have integrated a practical indicator of the real-time jitter into their
product, giving administrators an easy way to evaluate the hardware
and software. A system message during operation can draw attention to
incorrect states.
Start/stop behaviour
Depending on the setting, TwinCAT is started and stopped manually or
automatically. Since TwinCAT is integrated into Windows NT/2000/XP as
a service, an operator is not needed to start the system: switching
on is enough.
Restarting and data backup
When a program is started or restarted, TwinCAT loads programs and remanent
data. To backup data, and to shut down Windows NT/2000/XP correctly,
a UPS (uninterruptible power supply) is of great value.
TwinCAT and "Blue Screen"
The TwinCAT system can be configured such that real-time capability
is maintained in the event of a BSOD (Blue-Screen-of-Death) operating
system crash. Real-time tasks such as PLC and NC can therefore continue
to run and bring the controlled process into a safe state. Ultimately,
it is the decision of the programmer whether or not to utilise this
feature, bearing in mind that data or programs may already have been
destroyed by the BSOD.
World-wide connection through message routing - "remote"
connection is inherent to the system
According to the requirement for operating resources, the TwinCAT software
devices can be distributed: TwinCAT PLC programs can run on the PCs
or on Beckhoff Bus Terminal Controllers. A "message router"
manages and distributes all the messages, both in the system and via
TCP/IP connections. PC systems can be connected with each other via
TCP/IP; Bus Terminal Controllers are integrated via serial interfaces
and fieldbuses (Lightbus, PROFIBUS DP, CANopen, RS232, RS485, Ethernet
TCP/IP).
World-wide access
Since standard TCP/IP services of NT/2000/XP can be used, this data
can be exchanged across the world. The system offers scalable communication
capacity and timeout periods for the supervision of communications.
OPC provides a standardised means for accessing many different SCADA
packets. The SOAP (Simple Object Access Protocol) enables a connection
between two computers to be established by means of an internet connection
via standard HTTP. A TwinCAT component is available for this purpose
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