Process Unit 73 LF - Knick

Process Unit 73 LF
Interface Bus Protocol
Applies only if you have selected BUS coupling!
The protocol is based on a master/slave relationship. The participants addressed by the master (host
computer) are called slave. They have to execute the communication sequence as prescribed by the
controlling master.
Each communication sequence between participants on the bus is basically determined by two sections,
the command section and the response section:
In the command section the master defines meaning and function of the currently transferred message.
The command information is accepted by the slave and correspondingly evaluated.
The response section shows the master if a bus transfer has been properly executed. It can also contain
data, if required.
Data Format
Hardware: RS485 2-wire.
The data format is permanently set to 9600 bauds, 8 data bits, no parity.
Each slave has a bus address that may be in the range 01...31.
Each slave on a bus system must have a unique address.
The address 00 is a broadcast address (message to ALL).
Structure of a Message
1 Byte 1 Byte n Bytes 2 Bytes
slave address
status flags
length:
n + 2
ASCII message,
as with point-to-point connection,
but without message terminator
CRC16
according to
CCITT–X.25
12–30 Interface Commands