Functions
i-modul Modem 336 LL
6.7
IO Tunneling and Connection Safeguard
Every 20 seconds, or when the states of the digital inputs in the date stream change their
status, the i-modul Modem 336 LL 3.0 sends a test message to the i-modul Modem 336 LL
3.0 of the remote terminal. This test message is used to transmit the input states (IO
tunneling) and to perform a function check on the connection (connection safeguard).
The maximum frequency for state changes that are transmitted via IO tunneling is 0.5
Hz.
If the remote terminal responds to this test message within 120 seconds, the connection
is regarded as established and functional. If the test message is not responded to within
this timeframe in a regular manner, the i-modul Modem 336 LL 3.0 will re-attempt to
establish the connection. For the test message, a certain ASCII character is used. The AS-
CII character must be the same on each of the two devices of the leased line. We recom-
mend not using the test mark in the expected data traffic.
The default setting for the test mark for the connection safeguard is set to the ASCCI
character 3. IO tunneling and the connection safeguard are activated as default.
Configuration with AT commands
To completely switch the connection safe-
guard and the IO tunneling off, use the com-
mand
ATS8=0
To define the ASCII character for the connec-
tion safeguard and the IO tunneling, use the
command
Set a number between 1 and 255 instead of
<y>.
ATS8=<y>
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