User Manual
Operation
RFI-9256 Radio Modem User Manual Page 30 of 96
ESCAPE SEQUENCE
When there is no communications link established to a remote radio, and AT commands are issued locally
then the radio is in local command state.
When a connection is established to a remote radio, all communications occurs between the DTE’s
connected to the ports on the two radios. This is known as online state. Once a radio enters online state, it
assumes all the data sent to it is to be sent on to the remote radio, so it ignores all AT commands.
Unlike the other commands, there is no AT prefixing the escape sequence, and no carriage return after the
escape sequence. Instead, wait a full second before entering the three characters (default is ‘+’) typed
rapidly, then wait another full second. As soon as the radio returns to local command state, it will respond
with the message
OK
.
This delay period before and after the escape sequence is called the escape sequence guard time. This allows
the radio to distinguish the escape sequence from the normal flow of user information between radios.
The character used for the escape sequence is set in s-register 2, while the length of the escape guard time is
set in s-register 12.
When entering local command state, the connection is not disrupted. In order to return back to online state,
the command
ATO
is used.
HANGING UP
The
ATH
command is used to terminate a connection.
After communications has finished enter the escape sequence (+++). The radio responds with an
OK
message. Then execute the
ATH
command and the local radio will respond with
OK
. The remote radio will
output
NO CARRIER
as the communications link is lost.
DTR CONTROL OF HAYES STATE
The Data Terminal Ready (DTR) input to the radio can be used to control the Hayes dial-up state.
Ignore DTR:
The radio does not use the DTR signal to control its connection state.
Hang-up on DTR Low:
The radio will hang-up whenever the DTR line is low. If this option is
selected, and DTR is low when a remote radio is dialled then the connection will be terminated the
moment after it is established.
Hang-up on DTR Dropped:
The radio will hang-up whenever DTR changes from high to low.
Local on DTR Low:
Whenever DTR goes low, the radio will enter local command state. This is
the same as entering the escape sequence.
DIAL-UP NETWORKING WITH BACK-TO-BACK REPEATERS
A Hayes dial-up network can be extended by one or more back-to-back repeaters. In order to establish a dial-
up connection through a back-to-back repeater, an extension to the dialling system is used:
ATD<repeater
0
><repeater
1
>...<repeater
n
><address><extension><CR>