0049-2702-XXX Alliance Series Modems – USER MANUAL
08/05/2010
Rev. A
Page 119 of 197
with no more time between them than the guard time delay. The unit for this register is 1/50
second (or 20 ms), meaning that the default value of 50 equals 1 second.
If the guard time is zero, timing will not be a factor. The three escape characters can occur with
any timing relationship, but they must be consecutive. Be cautious when assigning small guard
times – you may not be able to enter three characters fast enough, especially if the guard time is
less than the time required to transmit one character at the current transmission rate.
S18 – Diagnostic timer
The value in register S18 determines how long a diagnostic test will
run. For example, if S18 is set to 120, the test (activated by one of the &T commands) will run
for 120 seconds. If S18 is set to zero, the default, the test timer will be disabled and the test will
run indefinitely. To terminate a test when the test timer is disabled, use the command
&T0
or
reset the modem. Register S18 is set to zero on powerup or by the command
AT Z
or
AT
S18=0
.
S25 – Delay to DTR
The value stored in register S25 determines how the ALX will respond to
a change in DTR. The response depends on the operating mode, as explained below.
Synchronous mode 1 (
&Q1
command):
The range for register S25 in this mode is 0-255
seconds
.
In this mode, the ALX initiates a call using asynchronous methods, but once the connection is
fully established, automatically switches to synchronous operation. A delay occurs after a
connection has been made before the modem examines the DTR signal. The length of this delay
is the value specified in S25 (in seconds). The delay allows the operator time to disconnect the
modem from an asynchronous data terminal and attach it to a synchronous terminal without
forcing the modem back into the command state.
Asynchronous mode (
&Q0
) and synchronous mode 2 (
&Q2
):
The range for register S25 in these modes is 0-255 x
0.01 second
.
Asynchronous mode is the default mode, suitable for most ALX operating modes. In
synchronous mode 2, when the ALX detects an OFF-to-ON DTR transition on pin 20, it
automatically dials the phone number stored in the phone cell displayed in the front panel
AUTO-DIAL screen. In asynchronous mode and synchronous mode 2 (after a connection has
been made), a change in DTR (ON or OFF) which lasts for less than the time specified in register
S25 (in 1/100ths of a second) is ignored by the modem.
S26 – RTS-to-CTS delay interval
This register affects synchronous operation only. With the
command
&R0
in effect, CTS is turned on in response to an OFF-to-ON transition of RTS from
the local DTE – after the delay specified by the value in register S26 (but only if the modem is
on-line and ready to receive synchronous data).
S Registers for Data Rate Control (Speed Limits)
S Registers S43, S44, S64 and S65 are used to set maximum and minimum data rates, as
indicated in the following table:
