Beckhoff BC8050, Документация

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RS232 - Interface
BC8050 und BC8150 77 Version: 3.0.0
6.1.3.2 KS8000 Communication Software
Fig. 60: Communication library icon
The Beckhoff KS8000 Communication Library provides functions with which it is possible to communicate
with the serial Bus Couplers (BK8000, BK8100, IP/ILxxxx-B8x0) easily via a serial PC interface. The KS8000
can be used as an OCX with all programming languages that use the Component Object Model (COM)
specifications from Microsoft (VC++, Visual Basic from version 4.0, Delphi, Java, etc). The KS8000 library
also has a DLL interface for any other C/C++ programs.
Accessing the process image
Via the serial PC interface the KS8000 enables access to the input and output process image of the BK8x00
Bus Couplers or the IP/ILxxxx-B8x0 Fieldbus Boxes.
With each serial PC interface, communication with
- a BK8100 coupler (RS232) or
- a Fieldbus Box IP/ILxxxx-B810 (RS232) or
- up to 99 BK8000 couplers (RS485) or
- up to 69 Fieldbus Boxes IP/ILxxxx-B800 (RS485)
can be established. Such communication transfers the whole of the input and output process image. The
communication duration therefore depends on the size of the process image. For example, with an RS232
coupler at 38400 baud and
• a process image of one word, the communication duration is approx. 6 ms;
• a process image of 15 words, the communication duration is approx. 20 ms.
Interface for LabVIEW applications
The KS8000 contains an interface for the LabVIEW programming software from National Instruments.
LabVIEW solutions consist of what are known as front panels, which serve as the man/machine interface,
and of a block diagram, which embodies the actual control program. KS8000 provides LabVIEW users with a
greatly simplified method of access to all the process data.
Operation of KS8000 or TwinCAT via the RS485COM port requires a PC card that automatically switches
between send and receive mode without echo (e.g. C9900-A440: RS 485 high speed with 2 serial interfaces,
optically decoupled, overvoltage protection, ISA bus).
6.2 Introduction to the system
6.2.1 Overview of the physical structure of RS232
The serial, asynchronous RS232C or V.24 communication interface is a widely used as a simple physical
connection for exchanging data between two systems. The RS232 interface only describes the physical
structure and not the protocol or the application layer.
The data are applied sequentially for the duration of one bit. Synchronization is based on start and stop bits.
Asynchronous data transfer requires no clock line. This means that a minimum of 3 lines are required, i.e.
one for sending, one for receiving, and one for GND. Since in each case one line is available for sending and
one for receiving, the technique is referred to as full duplex transfer. All devices can send or receive as
required, since they have a dedicated line available.
The RS232C or V.24 interface operates bipolar with +12 V / -12 V voltage level (+3 V...+12 V = "0" and
-3 V...-12 V = "1" ). The same baud rate, number of data bits, number of stop bits, and data verification of the
so-called parity bit have to be used on both sides. This is usually described as 9600, 8, e, 1 (i.e. 9600 baud,
8 data bits, even parity verification, one stop bit).