86
W&T Packetizing serial datagrams
racters is equal to the sum from the Length field and Additio-
nal Bytes, the datagram is passed to the network.
10�1�3 Interpacket Delay
The Com-Server structures the serial data stream based on a
configurable rest pause in ms for serial reception. This means
after receipt of any character the following data are collected
until no more characters have been received within the time
set as Interpacket Delay. Only now is the datagram passed
into the network.
n
Activate this Packet Option (Telnet)
Activates the selected option for serial data reception.
n
Interpacket Delay
Enter the desired Interpacket Delay in ms. The permissible
minimum value is 3ms. The tolerance is approx. 1 charac-
ter length, as results from the serial parameters which are
set.
1
Regardless of the configured Interpacket Delay the
Com-Server sends incoming data to the network-side
communication partner only once the set MTU is reached. The
factory default setting for this is 560 bytes. In the menu path
Setup System r Setup TCP/IP r MTU this can be extended to
1024 bytes.
Example
Modbus/RTU separates datagrams using a rest pause of at
least 3.5 character lengths. A baud rate of 9600 with data for-
mat 1 start bit + 8 data bits + 1 stop bit results in a character
length of approx. 1ms. For 3.5 character lengths this results a
rounded-off Interpacket Delay of 4ms:
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