Communications
configuring
System- and communication configuring D7-SYS - SIMADYN D
3-13
Edition 12.2003
The "Select" data transfer mode is used,
•
if information loss may not occur due to data being overwritten, and
•
if there can be as many transmitters as required for one receiver
"Select" defines a sequential channel processing. If the receiver
acknowledges that it has received the last data set, then the transmitter
deposits a new data set in the channel. A net data buffer is provided for
data transfer. A channel administrator controls the data transfer.
All of the configured transmitters use the same net data buffer. There is
no defined sending sequence for the transmitter. The first one sends first.
In order to achieve controlled data transfer, a "1" may only be specified at
one transmitter at the EN connection.
The transmitter must be configured in a shorter sampling time than the
receiver.
Trans. 1
KVL
NDP
Trans. 2
....
Trans. n
Receiver
KVL = channel
NDP =net data buffer
Fig. 3-3
Data transfer in the "Select" mode
The "Multiple" data transfer mode is used,
•
if receivers are to always be provided with the latest data, and
•
if as many receivers as required are available for each transmitter.
"Multiple" overwrites data when transferring data. The transmitter always
deposits the latest data set in the channel without the receiver first
acknowledging that it has received the last data set.
If a transmitter overwrites a buffer, from which a receiver is presently
reading, then the receiver rejects the data which were last received.
Receive is repeated in the next operating cycle.
There are two net data buffers for data transfer, which are used as
alternating buffer system. The transmitter flags in which buffer the latest
data are located.
The receivers must be configured in the same or shorter sampling time
than the transmitter (the receivers must therefore operate faster).
"Select" data
transfer mode
"Multiple" data
transfer mode
