Users Manual

C
C. Ethernet Modem Commands
A serial port on the NPort can be set to Ethernet Modem mode, allowing a PC or device to connect to the
NPort as if it was an Ethernet modem. This section provides additional detail about how the NPort operates
in Ethernet Modem mode.
Dial-in Operation
The NPort can listen for a TCP/IP connection request from a remote Ethernet modem or host. The NPort’s
response depends on the ATS0 value, as follows.
ATS0=0: The NPort will temporarily accept the TCP connection and then send the “RING” signal out
through the serial port. The serial controller must reply with “ATA” within 2.5 seconds to accept the
connection request, after which the NPort enters data mode. If no “ATA” command is received, the NPort
will disconnect after sending three “RING” signals.
ATS0
ʁ
ʁ
1: The NPort will accept the TCP connection immediately. It will send the “CONNECT {baudrate}”
command to the serial port and will immediately enter data mode.
Dial-out
The NPort accepts ATD commands such as “ATD 192.168.1.1:4001” from the serial port. It will then
request a TCP connection from the specified remote Ethernet modem or PC. Once the remote unit accepts
this TCP connection, the NPort will send the “CONNECT {baudrate}” command to the serial port and will
immediately enter data mode.
Disconnection Request from Local Site
When the NPort is in data mode, you can initiate disconnection by sending “+++”. Some applications allow
you to directly set the DTR signal to off, which will also initiate disconnection. The NPort will enter command
mode, and you can then enter “ATH” to close the TCP connection “NO CARRIER” will be returned to the
serial port.
ATTENTION
When entering “+++” to disconnect, the three “+” characters must be sent in quick succession, and the
sequence must be prefaced and followed by a guard time to protect the raw data. You can change the
disconnect character using register S2. You can set the guard time using register S12.
Disconnection Request from Remote Site
After the TCP connection has been closed by the remote Ethernet modem or PC, the NPort will send “NO
CARRIER” to the serial port and will return to command mode.