Trdatansmission Procedure With Data Point-To-Point Connection - Siemens SIMATIC CP 440 Manual

Basic Principles of Serial Data Transmission
2.2 Transmission Procedure with a Point-to-Point Connection
When data is transmitted, all communication partners involved must follow fixed
rules for handling and implementing the 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.
2.2.1 ISO 7-Layer Reference Model for Data Transmission
Protocol
All communication partners involved in data transmission must follow fixed rules for
handling and implementing the data traffic. Such rules are called protocols.
A protocol defines the following points:
Operating mode
Half-duplex or full-duplex mode
Initiative
Which communication partners can initiate data transmission and under what
conditions
Control characters
Which control characters are to be used for data transmission
Character frame
Which character frame is to be used for data transmission
Data backup
The data backup procedure to be used
Character delay time
The time period within which an incoming character must be received
Transmission speed
The transmission rate in bps
Procedure
This is the specific process according to which the data is transmitted.
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Point-to-point connection CP 440 Installation and Parameter Assignment
A5E00057742-02