Supported Hardware

KL6xxx in 3-Byte Mode

The standard version, as supplied, of the Beckhoff serial bus terminal is operated in 3-byte mode. In other words, a bus telegram can transmit or receive 3 data bytes to or from the terminal. Since every data exchange between the PLC and the bus terminal requires 3 PLC cycles, the effective transfer rate is one byte per cycle.

The maximum effective data transfer rate in bits per second (Bps) depends on the cycle time, T, of the PLC, and on the number of useful bits in each data byte transferred, LB:

Bps = LB / T

LB = 1 start bit n data bits p parity bits m stop bits

The maximum effective data transmission rate is limited by the physical baud rate programmed into the terminal.

Note: Pay attention to the K-Bus update time if bus terminals KL6xxx and bus couplers BKxxxx are used (Task Configuration).

KL6xxx in 5-Byte Mode

The serial bus terminal can be reprogrammed offline by means of a configuration program (Beckhoff KS2000), so that, in 5-byte mode, 5 data bytes at a time can be transferred to or from the terminal. 3 PLC cycles are still necessary for each exchange. The effective data rate for a given cycle time is thus 5/3 greater than in 3-byte mode.

Bps = (LB * 5/3) / T

The bus terminals cannot be re-programmed while the PLC is running, since the 3-byte and 5-byte modes differ in the register mapping and in the TwinCAT System Manager configuration. For this reason, the required re-programming means that 5-byte operation is only recommended for time-critical applications.

Note: Pay attention to the K-Bus update time if bus terminals KL6xxx and bus couplers BKxxxx are used (Task Configuration).

KL6xxx in 22-Byte Mode

The serial bus terminal can be reprogrammed offline by means of a configuration program (Beckhoff KS2000), so that, in 22-byte mode, 22 data bytes at a time can be transferred to or from the terminal. 3 PLC cycles are still necessary for each exchange. The effective data rate for a given cycle time is thus 22/3 greater than in 3-byte mode.

Bps = (LB * 22/3) / T

Note: Pay attention to the K-Bus update time if bus terminals KL6xxx and bus couplers BKxxxx are used (Task Configuration).

EL60xx in 22-Byte Mode

The serial EtherCAT terminal is operated in 22-byte mode, so that 22 data bytes at a time can be transferred to or from the terminal. 3 PLC cycles are still necessary for each exchange.

Bps = (LB * 22/3) / T

Terminals' parameterization will be conducted by the CoE-Online tab in the TwinCAT System Manager (double-click on the referring object).

Serial PC Interface

The serial PC interface (COM1, COM2 etc.) is handled by the TwinCAT system similarly to the serial bus terminal, but use larger data transfer buffers than the serial bus terminal. The library uses a 64 byte buffer, so up to 64 data bytes are transferred at once between the PLC and the interface driver. 3 PLC cycles are again needed for the exchange of a data block with the serial PC interface.

Bps = (LB * 64/3) / T

Virtual Serial COM Port

A virtual serial COM port (COM1, ..., COM255) which is available in Windows is also supported by the TwinCAT system. No configuration in the TwinCAT System Manager is needed.
The parameterization is done directly in the PLC with the given function blocks.

The communication interface is not real-time capable.

Communication baud rates are available from 150 baud up to 115200 baud.

Note: The product is devoloped for applications with one virtual COM port per target system. The usage of more than one virtual COM port is with function test generally possible.