Modem Configuration - Sena STS Series User Manual

the internal buffer. The STS 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 STS
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 STS Series internal
buffer size. The serial communication buffer size of STS Series is 256 bytes.

4.2.9. Modem configuration

The STS Series supports direct modem connection to the serial port of it. When user wants to connect
modem to a serial port, he must configure Modem init-string and DCD behavior on modem
configuration page. The STS Series supports modem connection only when host mode is set as TCP
mode.
Enable/Disable modem
By enabling this menu, user can attach a modem directly to the serial port of STS Series. If this
parameter is enabled, STS Series considers this port will be used for modem use exclusively.
Modem init-string
User can specify modem initialization string for his modem in Modem init-string parameter. When
a serial port is set as modem mode by setting Enable/Disable modem parameter as Enabled,
STS Series sends modem initialization string to the serial port whenever rising edge of DTR pin is
detected or parameter related with serial port configuration is changed.
DCD behavior
If DCD behavior is set as Allow TCP connection only by HIGH, STS Series permits a connection
from the remote host only when the DCD status of serial port is high. This feature is useful when
user want to use a serial port only for dial-in modem mode. In this case, if there is no connection
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