WI-GTWY-9-xxx Wireless Gateway V1.18
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4.9
Fieldbus Configuration
All WI-GTWY-9-xxx modules (
except MD1
) have separate internal hardware comprising the
Fieldbus Interface, consisting of a separate microprocessor and appropriate hardware for the
network connection. This Fieldbus Interface handles all fieldbus communications, and transfers
I/O in the Fieldbus Interface Registers to/from the fieldbus. Conversely, the WI-GTWY-9-xxx
Radio Interface handles all radio communications, and transfers I/O in the Radio Interface
Registers to/from the radio network. For I/O transfer between the radio network and the fieldbus
network, I/O Registers in the Radio Interface must be linked with registers in the Fieldbus
Interface using configuration software.
Depending on the fieldbus protocol, the size of the Fieldbus Interface may be limited (for
example, the Profibus Slave interface supports only 416 bytes I/O). The Radio Interface
supports 10,000 registers, of which 4300 are general-purpose I/O registers. Each Radio Interface
register is 16-bit, even for discrete (or “digital”) input or output values. The Fieldbus Interface
comprises a block of 8-bit bytes (referred to as “locations”). Digital I/O can be packed - each
fieldbus location can hold 8 digital inputs or outputs. Analog or pulse values can be stored as a
low resolution 8-bit value (a single fieldbus location) or as a high resolution 16-bit value (two
consecutive fieldbus locations).
To optimize I/O usage, the WI-GTWY-9-xxx provides a flexible method of data transfer between
the Radio Interface and the Fieldbus Interface. The user configures
links
between the Radio
Interface and Fieldbus Interface via
Fieldbus Mappings
in the WI Series Configuration Software.
The diagram shows in more detail the relationship between the Radio Interface and Fieldbus
Interface.
WRITE
RADIO
INTERFACE
I/O
DATABASE
I/O REGISTERS
FIELDBUS
LOCATIONS
READ
FIELDBUS
INTERFACE
RADIO
DRIVER
DATA BUS
ANTENNA
