VSCOM NetCom Plus 111, Руководство пользователя

Страница: 97 / 133

8 IP Modem Function
The recommended cable connects as shown in this table. Please note, this installation does not
use the simply crossed signals. Especially the DSR of the PC is internally connected to the DTR
of the PC.
DB9m PC IP-Modem DB9m DB9f
3 TxD —— RxD 2 3
2 RxD —— TxD 3 2
7 RTS —— CTS 8 7
8 CTS —— RTS 7 8
6 DSR PC-DTR (internal loop-back)
4 DTR —— DSR 6 4
1 DCD —— DTR 4 6
5 GND —— GND 5 5
Table 19: IP Modem cable
The limitation of signals is a restriction in function, compared to real world serial modems. Since
most installations do not require the full availability of all signals, the required subset can be
selected.
8.3 Operation Modes by IP Modem
The function of IP-Modem may be configured port by port. On a NetCom
+
with a single port
there is no much of a difference. However a NetCom
+
with more serial ports operates each port
independently. In the following sections of this manual the phrase "serial port of a NetCom
+
,
configured to operate as IP Modem" is replaced by "IP Modem" for brevity.
Two basic operation modes are available. The first and default mode is Modem-to-Modem. This
requires a serial port of a NetCom
+
configured as IP Modem on both ends of the connection.
When one IP Modem dials the other, the connection is established on the TCP level. Directly
afterward both IP Modems negotiate to ensure they are a real NetCom
+
IP Modem and are free
for connection. If successful both issue a "CONNECT . . . " response to the serial connected devices.
This is convenient for the customer to understand. The CONNECT may report some parameters,
e.g. the minimum serial speed used by both Modems. These extra parameters are not implemented
so far.
The other mode is named as Modem-to-Host. The destination is any software, which opens a TCP
port for Listen mode. It may be a second NetCom
+
configured for TCP Raw Server Mode. It may
also be the customers application, running on a certain computer. This mode offers less features.
8.4 Hayes Commands
The IP Modem operates with a command set similar to those in real Modems. All of the commands
start with the character sequence AT.
September 2016 NetCom Plus User Manual 97