5
Serial communication protocols
5.1 Overview
The simplest type of information exchange between two stations is the point-to-point link.
Here the CP serves for the interface between a host system and a communication
partner. The data are serially transferred. During the serial data transfer the individual bits
of one byte of an information are transferred after another in a fixed order.
At bi-directional data transfer it is differentiated between
full-duplex
and half-duplex oper-
ation. At
half-duplex
operation at one time data may be sent or received. A simultaneous
data exchange is only possible at
full- duplex
operation. Each character to be transferred
is preceded by a synchronizing pulse as
start bit
. The end of the transferred character is
formed by the
stop bit
. Beside the start and stop bit there are further parameterizable
agreements between the communication partners necessary for serial data transfer.
This character frame consists of the following elements:
n
Transfer speed (Baud rate)
n
Character and acknowledgement delay time
n
Parity
n
Number of data bits
n
Number of stop bits
The CP serves for an automatic serial data transfer. To do this the CP is equipped with a
driver for the corresponding protocols.
The following protocols are described:
n
ASCII
n
STX/ETX
n
3964(R)
n
Modbus (Master, Slave)
Serial transfer of a char-
acter
Character frame
Protocols
VIPA System SLIO
Serial communication protocols
Overview
HB300 | CP | 040-1CA00 | en | 18-28
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