User manual

Chapter 1 Introduction
Page 13 ©February 2009
An “output” is a value coming into the 105G via the fieldbus. An input is a value going out from
the 105G via the fieldbus.
So a Modbus Plus 105G can handle up to 4300 I/O total, but analog or pulse inputs are limited to
1024 x 16-bit values. The same limit applies to outputs.
The Modbus Plus interface allows global data base transactions with routing for up to six
Modbus Plus networks.
1.2 The 105G Structure
The 105G has three functional sections:
• The Radio Interface consists of an I/O database (or "Process Image") that maintains the latest
values of all I/O in the wireless I/O system. The I/O database comprises 4300 x 16 bit I/O
registers and 4300 x 16 bit status registers. There are also other registers in the database that
can be used for system management - they are discussed later in this manual. NOTE – the
terms ‘Radio Interface’ and ‘I/O database’ are used interchangeably throughout the manual.
• The radio port allows the 105G to communicate with other 105G and/or 105U modules using
a proprietary radio protocol called “WIB-net”. Messages from the 105U modules are received
by the radio port and used to update the input values in the 105G Radio Interface. The radio
port also creates the correct radio message to set outputs on the remote 105U modules.
The WIB-net 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 WIB-net 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 105G 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.
FIELDBUS
INTERFACE
FIELDBUS
PROFIBUS
ETHERNET
MODBUS
DEVICENET
MODBUS +
RADIO
PORT
RADIO
INTERFACE
I/O
DATABASE
RADIO
INTERFACE
Gateway
ON-BOARD I/O
EIGHT DISCRETE I/O SIGNALS
DF1
MODBUS RTU