Filter
Top Products
7.6 Using a modem in ATMODE
In this mode the Hayes set of commands is used, all of which begin with the letters AT.
Both call setup and configuration are performed using these commands.
The commands can be configured on the DVST unit in setup mode.
The modem is also controlled using DTR (Data Terminal Ready), and indicates it’s
status using DCD (Data Carrier Detect).
Call request
The DTR is normally active, unless the modem channel is turned off, or the unit is in
setup mode.
To dial a call the system sends the dial string (set by DIAL= in the DVST setup menu ) to
the modem, followed by the number selected.
For synchronous operation the modem switches to synchronous mode on connection.
When the call connect has been completed the modem raises it’s DCD line, confirming it
is connected with the remote location. A call already being active is indicated by the
DCD line being active (high) from the modem.
Call answer request
If a call is incoming, and the DTR line is high, the modem answers the call, establishes
the physical link, and then raises DCD to inform the DVST unit that a call is present.
Call disconnect
This is requested by a high to low transition on DTR. A successful
disconnect is confirmed by the DCD line being dropped by the modem.
In this mode the DTR returns high after a short delay.
7.7 General settings for modems in ATMODE
The modem is configured from the DVST unit using the following strings:
MINIT=general modem configuration.
SREG=typically used for setting of s-registers.
USER=optional string, typically for individual customisation.
DIAL=string used to dial, typically ATDT for tone dialling.
The configuration details stored in MINIT, SREG & USER are sent on power-up, leaving
setup mode, and on disconnecting a call. If a MODEM is not present a large delay will be
experienced while the system waits for replies from the MODEM. To avoid this the
command MODEM=OFF should be selected from the DVST setup menu. It is also
possible to transmit or send these values to the MODEM using the SEND command in
setup.
It is also possible to communicate with the modem directly using the MODEM
command.
Dedicated Micros Ltd Page 23
DVST Installation Guide Modems