Westermo RM-455U-D - Manual (Page 43)

455U-D Radio Modem User Manual
Page 44 © May 2010
3.7.2 Auto Answer (Auto-Connect Slave)
The only configuration required for an auto-connect slave module is to enter its unit address.
Its address path will be automatically
taken from the Connect message from
the master unit.
If you enter an “Inactivity Timeout”
value, then the 455U-D will
automatically reset the link if there has
been no data transmission within this
time. If you use the link check feature
at the master unit, you should enter an
“Inactivity Timeout” value to reset the
link at the slave unit.
It is a good idea to use these timers as
it provides a higher level of security for the Acknowledged mode system. Normally a link
check time will be entered at the master unit (for example, 10 seconds), and an inactivity
timeout will be entered at the slave unit (for example, 15 seconds). It is important that the
inactivity timeout is greater than the link check time.
A value of zero disables these parameters.
3.7.3 Single-Connect Acknowledged mode
Single-connect is similar to a dial-up telephone modem. In this mode, the module will
attempt to connect to a destination address once. A host device will issue a connect “dial”
(ATD) command, and the module will send a connect message to the destination address. If
the destination module responds, then the link is connected and the unit goes online. The
DCD status is set (LINK LED comes on, DCD signal and DIO signal turn on if configured).
If the destination module does not respond, then the initiating modem will re-try (up to the
number configured in S-Register S7). If there is no response, the link is not established and no
data can be transferred. The module will not attempt to reconnect again until it receives
another connect command from its host.
The link is normally disconnected by the host issuing a disconnect or “hang-up ATH
command. In this mode, it is normal for a host to connect and disconnect to several slave
modules using AT commands. A common example is a PC polling several analyzers or
dataloggers. The PC connects to a remote station one at a time, transfers data, disconnects
and connects to the next station.
Up to six repeater addresses may be configured as part of the remote address. That is, up to 6
intermediate modules can act as repeaters between the master and slave modules.
The RS232 DTR signal can be configured to act as a disconnect signal. If so configured
(AT&D), the DTR signal will force a hang-up (DCD reset) if the host device resets the
DTR signal.
In single-connect Acknowledged mode, the host devices use AT commands to select
destination addresses to connect to. Normally only a unit address is required.