WI-GTWY-9-xxx Wireless Gateway
Introduction v1.18
14
9-xxx Radio Interface. The radio port also creates the correct radio message to set outputs on
the remote WI-I/O 9-x modules.
The WI-I/O 9-x protocol is an extremely efficient protocol for radio communications. Radio
messages can be sent using exception reporting - that is, when there is a change of an input
signal - or by read/write messages. Each message can comprise a single I/O value, or multiple
I/O values (termed a “block” of I/O). There are also update messages, which are sent for
integrity purposes. Messages include error checking, with the destination address sending a
return acknowledgment. Up to five attempts are made to transmit the message if an
acknowledgment is not received. The WI-I/O 9-x protocol is designed to provide reliable
radio communications on an open license-free radio channel.
•
The Fieldbus port enables communications between a host device, which could be a PLC,
DCS, HMI, intelligent transducer, etc), and the WI-GTWY-9-xxx Radio Interface database. A
“host device” may be one or several devices connected to the same fieldbus or network (for
example, an Ethernet LAN) - in this manual, the LAN is considered as a “host device”.
The fieldbus port decodes messages from the host device and reads or writes I/O values to the
database. The fieldbus port can also generate messages to the host device.
The WI-GTWY-9-xxx I/O database effectively isolates the fieldbus and the radio network. This
provides a high level of system performance. The WI-I/O 9-x radio protocol is very efficient and
reliable for radio communications. It minimizes radio channel usage by "change-of-state"
reporting, and allows the use of intermediate repeater addresses. It also allows peer-to-peer (WI-
I/O 9-x to WI-I/O 9-x, WI-GTWY-9-xxx to WI-GTWY-9-xxx) and peer-to-master (WI-I/O 9-x
to WI-GTWY-9-xxx) communications. PLC protocols, by comparison, are designed to provide
transfer of large I/O files by "wire" link. The WI-GTWY-9-xxx retains the advantage of both
protocols in their respective communications media.
1.2.1
On-board I/O
The WI-GTWY-9-xxx has eight on-board discrete I/O. Each I/O point can be used as either a
discrete input (voltage free contact input) or discrete output (transistor output) - an I/O point
cannot be used as both input and output. Each I/O point is linked to two separate I/O registers in
the database - one for the “input” function and one for the “output” function.. If the output
register is set “on” by the fieldbus or by a radio message from a remote module, then the WI-
GTWY-9-xxx will automatically set the input register for the same I/O point to “off”. This means
that the output register has priority over the input register - if there is a conflict, the input value is
ignored.
The WI-GTWY-9-xxx also has three internal inputs linked to I/O registers:
♦
Supply voltage status - if the normal supply fails, this status is set on.
♦
Low battery voltage. The WI-GTWY-9-xxx has an internal battery charger to trickle charge a
back-up battery. If the battery voltage is low, this status is set.
♦
Battery voltage - the actual value of the connected battery voltage.
1.2.2
I/O Expansion - WI-I/O-EX-1-S-xx modules
