105U-G Wireless Gateway
User Manual
Page 123
© September 2004
The 105G Modbus Plus supports up to 1024 words of output data and 1024 words of input
data. Converting this to 40000 registers, the possible output registers (Data To Network)
range is 40001 – 41024 of which the first 32 words (i.e. 40001 – 40032) are global output
data. However all output registers, including the global output registers, may also be read
from the module using the point-to-point command Read Holding Registers (0x03). The
possible input registers (Data From Network) range is 41025 – 42048 of which the first 32
words (i.e. 41025 – 41056) is global input data (i.e. data extracted from another network
device’s global output data). Only data
not
assigned to global input data (i.e. 41057 – 42048)
may be written by the point-to-point preset register commands.
4.13.4
Configuration
Fieldbus mappings are made to Anybus “words” - that is, the input and output bytes in the
Anybus interface are pre-grouped into 16-bit words to fit the Modbus format.
The “Node Address” will be the Modbus Plus network address of the 105G, (allowable
values are 1 – 64) and must be unique for the network segment. The “Source Address” will
be the Modbus Plus network address of another module on the network from which the 105G
will extract Global Data (i.e. Data From Network). “GDB I/P Count” (up to 32 words max)
specifies the amount of Global Data to extract from the “Source Address” each cycle. An
offset into the source unit’s global data (“GDB I/P Offset”) may also be specified in order to
read a specific portion of the 32 word global data of the source address. However, since only
32 words max of global data are produced, the sum of GDB I/P Offset and GDB I/P Count
must never exceed 32. After setting these parameters, the 105G I/O Registers must be linked
to Modbus Plus 40000 registers with appropriate “Fieldbus mappings”.
In the below example there is one “Fieldbus Write Mapping” (this will make available Data
To Network) and one “Fieldbus Read Mapping” (this will make available Data From
Network). When adding mappings, software will automatically adjust the available 40000
register address range depending on the command type (i.e. read or write fieldbus mapping),
see below.
The I/O Register selection below for the fieldbus read mapping shown above, illustrates the
allowable 40000 register address range base upon the chosen command type.
