Transmission Mode In Point-To-Point Communication - Siemens SIMATIC CP 340 User Manual

Basic Principles of Serial Data Transmission

2.2 Transmission mode in Point-to-Point Communication

2.2 Transmission mode in Point-to-Point Communication
Introduction
When data are transmitted, all communication partners must adhere to a fixed set of rules for
handling and implementing data traffic. The ISO has defined a 7-layer model, which is
recognized as the basis for a worldwide standardization of transmission protocols for
computer-to-computer communication.
ISO 7-Layer Reference Model for Data Transmission
All communication partners must adhere to a fixed set of rules for handling and implementing
data traffic. Such rules are called protocols.
Protocol
A protocol defines the following points:
● Operating mode
● Initiative
● Control characters
● Character frame
● Data backup
● Character delay time
● Transmission speed
Procedure
This is the specific process according to which the data is transmitted.
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Half-duplex or full-duplex operation
Which communication partners can initiate the transmission and under what conditions
Which control characters are to be used for data transmission
Which character frames are to be used for data transmission.
The data backup procedure to be used
The time period within which an incoming character must be received.
The baud rate in bits/s
PtP coupling and configuration of CP 340
Manual, 04/2011, A5E00369892-03