Chapter 4 Configuration
MAN_105G_1.5 Page 54
To enter a Modbus command, select “New Serial Mapping”. The following example is a
digital write command which writes 105G I/O registers 20 – 25 (6 registers) to Modbus
outputs 00012 – 00017, at Modbus Slave address 1.
The entry under “I/O Register” is the first I/O register in the 105G to be transferred - the
“I/O count” is the number of registers to be transferred. If the selected Modbus slave does not
respond to the command, then the 105G will write a ‘FFFF’ value to one of its own registers,
configured under “CF Register” - in this case it is register 4800.
The “Command Type” selected is a write command (you can select read or write) - which
means that the values are sent from the 105G to the Modbus Slave. The type of write
command is a “Digital” write, meaning that the register values will be written as digital/binary
values”.
If the Modbus Slave device does not respond to the Modbus command, the 105G will try
another 3 times (“Max Retries” = 3). The Modbus command will be sent to the Modbus
Slave every 100msec.
The address of the Modbus Slave is 1 (permissible addresses are 1 – 255). Because a digital
write command has been selected, the destination register type will be digital outputs, with
Modbus tag “0xxxxx”. The first destination Modbus location is 12 (or 00012) - as there are
6 registers transferred, the destination locations will be 00012 – 00017.
The second example is a register read command to the same Modbus Slave (address 1). The
command requests the Modbus Slave to return the values of 10 registers which will be stored
in I/O registers 463 - 473 in the 105G. As the command is a “register read” command, the
target Modbus locations will be of the type 3xxxx. The starting location is 30001. So the
values of locations 30001 – 30010 in Modbus Slave 1 will be transferred to I/O registers 463
– 473 in the 105G.
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