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Communication protocols
Overview
6
Communication protocols
6.1 Overview
Serial transfer of a char-
acter
Character frame
Protocols
36
n
The simplest type of information exchange between two stations is the point-to-point
link. Here the CP serves as interface for the CPU and a communication station.
n
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.
n
At half-duplex operation at one time data may be sent or received.
n
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 nec-
essary for serial data transfer.
This character frame consists of the following elements:
n
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
drivers for the following protocols:
n
ASCII
n
3964(R)
Please regard the computer interface RK512 is not supported by the
VIPA CP 341-1CH01.
Additionally the following loadable protocol driver are supported:
n
Modbus master RTU
n
Modbus master ASCII
Modbus slave RTU
n
In the following each supported protocol is described.
When using loadable drivers for software technical reasons transfer
driver from Siemens to the CP, but not installed there. As in the CP
341-1CH01 VIPA own drivers are installed, is the use of Siemens usual
hardware dongles not required.
VIPA System 300S
Ä Chap. 6.2 'ASCII' page 37
HB130 | CP | 341-1CH01 | en | 18-40
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