C
C
Appendix 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
≧
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.