13.11 Installation → MODBUS client I/O Setup
Sequential mode
Available only when Show Advanced Options (see 13.11) is selected. Selecting this check-
box forces the modbus client to wait for a response before sending the next request.
This mode is required by some fieldbus units. Turning this option on may help
when there are multiple signals, and increasing request frequency results in signal
disconnects. Note that the actual signal frequency may be lower than requested
when multiple signals are defined in sequential mode. Actual signal frequency can
be observed in signal statistics (see section 13.11). The signal indicator will turn
yellow if the actual signal frequency is less than half of the value selected from the
"Frequency" drop-down list.
Add signal
Push this button to add a signal to the corresponding MODBUS unit.
Delete signal
Push this button to delete a MODBUS signal from the corresponding MODBUS
unit.
Set signal type
Use this drop down menu to choose the signal type. Available types are:
• Digital input: A digital input (coil) is a one-bit quantity which is read from the
MODBUS unit on the coil specified in the address field of the signal. Function
code 0x02 (Read Discrete Inputs) is used.
• Digital output: A digital output (coil) is a one-bit quantity which can be set to
either high or low. Before the value of this output has been set by the user, the
value is read from the remote MODBUS unit. This means that function code
0x01 (Read Coils) is used. When the output has been set by a robot program or
by pressing the “set signal value” button, the function code 0x05 (Write Single
Coil) is used onwards.
• Register input: A register input is a 16-bit quantity read from the address
specified in the address field. The function code 0x04 (Read Input Registers)
is used.
• Register output: A register output is a 16-bit quantity which can be set by the
user. Before the value of the register has been set, the value of it is read from
the remote MODBUS unit. This means that function code 0x03 (Read Holding
Registers) is used. When the output has been set by a robot program or by
specifying a signal value in the “set signal value” field, function code 0x06
(Write Single Register) is used to set the value on the remote MODBUS unit.
Set signal address
This field shows the address on the remote MODBUS server. Use the on-screen
keypad to choose a different address. Valid addresses depends on the manufacturer
and configuration of the remote MODBUS unit.
Version 3.4.5
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