Chapter 3
Installation
MAN_105G_1.16
Page 66
To complete the Fieldbus Configuration, enter any other Modbus commands that may be
required to transfer I/O points between the 105G and the Modbus Slave devices.
Digital I/O
The value of a digital I/O point is stored in the 105G database as a hexadecimal '0000' (“off”) or
hex 'FFFF' (“on”). However the 105G will generate either a ‘0’ (“off”) or ‘1’ (“on”) to a digital
output point (Coil) when sending commands to a Modbus slave - these are commands 05 and
15. Similarly, the 105G will accept ‘0’ or ‘1’ from the Modbus slave in response to a digital
read command and store ‘0000’ or ‘FFFF’ in the database location - these commands are 01 and
02.
Analog I/O
Analog I/O from the remote 105U modules are 16 bit register value. A value of 8192 (hex
2000) represents 0mA. A value of 49152 (hex C000) represents 20mA. Each mA has value of
2048 (hex 0800) - a change of 4096 (hex 1000) is equivalent to a change of 2mA. A 4-20mA
signal will vary between 16384 (hex 4000) and 49152 (hex C000). A 0-20mA signal will vary
between 8192 (hex 2000) and 49152 (hex C000).
Pulse I/O
Pulse counts from the remote 105U modules are shown as a 16-bit register. When the
register rolls over, from ‘FFFF’ (hex), the next value will be ‘0001’. The register will only
have a value of ‘0000’ when the remote module starts up, and the previous count is lost. This
value will indicate that the counter has reset.
Modbus Retry Delay
The 105G Modbus Master configuration includes a feature to limit the frequency at which slave
devices are polled for data. The 105G will poll each Modbus slave in order. If there is no delay