Siemens SIMATIC CP 340 - Basic Principles of Serial Data Transmission

PtP coupling and configuration of CP 340
Manual, 04/2011, A5E00369892-03
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Basic Principles of Serial Data Transmission
2
2.1 Serial Transmission of a Character
Introduction
The system provides various networking options for the exchange of data between two or
more communication partners. The simplest form of data interchange is via a point-to-point
connection between two communication partners.
Point-to-point communication
In point-to-point communication the communications processor forms the interface between
a programmable controller and a communication partner. In PtP communication with
communication processor, data are transferred via serial interface.
Serial Transmission
In serial transmission, the individual bits of each byte of information are transmitted one after
the other in a fixed order.
Unidirectional/Bidirectional Data Traffic
The CP 340 itself handles data transmission with communication partners via the serial
interface. The CP 340 is equipped with three different drivers for this purpose.
● Unidirectional data traffic:
– Printer Driver
● Bidirectional data traffic:
– ASCII driver
– 3964(R) procedure
The CP 340 handles data transmission via the serial interface in accordance with the
interface type and the selected driver.
Unidirectional Data Traffic - Printer Output
In the case of printer output (printer driver), n bytes of user data are output to a printer. No
characters are received. The only exception to this are data flow control characters (e.g.
XON/XOFF).