SENA SS800 - Manual (Page 63)

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 DTR/DSR behavior
The purpose of the DTR/DSR pin is to emulate modem signal control or to control TCP connection
state by using serial port signal. The DTR is a write-only output signal, whereas the DSR is a read-only
input signal in the Super Series side.
The DTR output behavior can be set to one of three types: always high, always low or high when open.
If the DTR behavior is set to high when open, the state of the DTR pin will be maintained high if the
TCP connection is established.
The DSR input behavior can be set to one of two types: none or allow TCP connection only by high. If
user sets the DSR input behavior as Allow TCP connection only by HIGH, TCP connection to remote
host from Super Series is made only when the DSR status is changed from low to high. And TCP
connection to remote host is disconnected when the DSR status is changed from high to low. And also
Super Series accepts TCP connection from the remote host only when the DSR status is high. In case
of UDP mode, Super Series receives UDP data from the remote host only when the DSR status is high.
In modem emulation mode, the connection to the remote host will be disconnected regardless of the
current DSR input behavior option if the DSR status goes to low.
Note: DTR/DSR behavior menu will not be shown when the modem is enabled.
 Inter-character timeout
This parameter defines the interval that the Super Series fetches the overall serial data from its
internal buffer. If there is incoming data through the serial port, the Super Series stores data into the
internal buffer. The Super Series transfers data stored in the buffer via TCP/IP, only if the internal
buffer is full or if the inter-character time interval reaches to the time specified as inter-character
timeout. If inter-character timeout is set as 0, then data stored in the internal buffer will be transferred
immediately without any delay.
Optimal inter-character timeout would be different according to your application but at least it must be
larger than one character interval within specified baud rate. For example, assume that the serial port
is set to 1200 bps, 8 Data bits, 1 stop bit, and no parity. In this case, the total number of bits to send a
character is 10 bits and the time required to transfer one character is
10 (bits) / 1200 (bits/s) * 1000 (ms/s) = 8.3 ms.
Therefore, you have to set inter-character timeout to be larger than 8.3 ms. The inter-character
timeout is specified in milliseconds.
If users want to send the series of characters into a packet, serial device attached to the Super Series
should send characters without time delay larger than inter-character timeout between characters and
the total length of data must be smaller than or equal to the Super Series internal buffer size. The
serial communication buffer size of Super Series is 256 bytes.