EUCHNER CIS3A-Mini - Manual (Page 8)

EUCHNER Identsystem CIS3A-Mini
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3.2 Special features of the data transfer protocol 3964R [1]
The 3964R data transfer protocol is a comparatively reliable program for electronic data
interchange between a control and a connected peripheral since data transfer is handled with
a standardised protocol.
On controls with integrated 3964R driver (see [1] for instance), it is not necessary for the
user to bother with the details of connection set-up and clear down respectively pay attention
to data integrity. It suffices to transfer the telegram core to the 3964R driver via the program.
On controls without 3964R driver or if a Electronic-Key-System is connected to a PC, the
user must, however, also program the connection set-up and clear down as well as the retry
attempts.
3.2.1 Basic information on data transfer procedures with protocol [1]
Numerous conventions must be agreed upon for a data transfer procedure: Codes, operating
modes, transfer speeds and the algorithmic transfer sequence. The stipulation of the
algorithmic sequence is referred to as transfer protocol (protocol for short). A transfer
protocol generally defines the following phases of data transfer:
· Connection establishment: Request from A to B for data transfer
· Data transfer from A to B
· Connection termination: End of data transfer
3.2.2 The transfer protocol 3964R [1]
Unlike non-protocol-based data transfer procedures, 3964R is a data transfer procedure with
protocol. This means that the actual data to be transferred is enclosed in specific control
characters. The 3964R driver allows comparatively reliable data transfer by virtue of the fact
that the receiver must first signal to the transmitter that it is ready to receive (connection set-
up) and, after data interchange, must acknowledge correct reception. Data integrity is
enhanced by an additional block check character with the 3964R transfer protocol.
The 3964R driver interprets the following control characters:
· DLE (10
hex
) Data Link Escape
· STX (02
hex
) Start of Text
· NAK (15
hex
) Negative AcKnowledgement
· ETX (03
hex
) End of Text