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VIPA System SLIO
5
Serial communication protocols
5.1 Overview
Serial transfer of a char-
acter
Character frame
Protocols
HB300 | CP | 040-1CA00 | en | 18-28
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 communication protocols
Overview
57
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