HEIDENHAIN TNC 306 Technical Manual - Manual (Page 417)

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TNC 406/TNC 306 1 Introduction 3/97
1.1 Principles of data transfer
Since all information is conveyed as data, one first needs to become familiar with a few of the
principles of data transfer. The term
data is used to describe all of the information which the
computer is capable of collecting and processing.
1.1.1 Serial/parallel
Data can be transmitted in either serial or parallel format.
Data in a computer system is coded, e.g. as bytes (8 bits), and supplied to the interface in parallel.
In the case of serial data transmission, the parallel information from the computer system has to be
converted into a serial data-flow by using a USART (Universal Synchronous/Asynchronous
Receiver/Transmitter).
The receiver accepts the serial data-flow and converts it back again into parallel information.
0 1 1 0 1 0 1 1
Sender
Transmitter
Speicher
Memory
Übertragungsstrecke
Transmission path
Empfänger
Receiver
Schnittstellen-Puffer
Interface buffer
MSB
LSB
0
1
1
0
1
0
1
1
0
1
1
0
1
0
1
1
MSB
LSB
0
1
1
0
1
0
1
1
0
1
1
0
1
0
1
1
Speicher
Memory
Schnittstellen-Puffer
Interface buffer
A parallel interface, on the other hand, does not need a USART, just a line driver. The computer
system and the peripheral are usually connected with a 36-pole ribbon cable. The maximum cable
length is generally about 3 metros.