User's Manual

455U-D Radio Modem Module User Manual
Page 44 © Jan 2008
Z3 stores the address that RS-485 messages are sent to.
Auto-Connect Slave
The only configuration required for
a auto-connect slave module is to
enter its unit address.
It’s 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
transmissions 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 a 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.
3.7.2 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.