Setup & Operation 12. Option Units
RC180 Rev.17 79
12.3 Fieldbus I/O Board
12.3.1 Overview of Fieldbus I/O
The Fieldbus I/O option is an option to add fieldbus slave function (DeviceNet,
PROFIBUS-DP, PROFINET, CC-Link, EtherNet/IP) to the robot Controller.
A fieldbus is a standard of signal communications between field devices operating in a
factory (sensor, actuator, robot controller, etc.) and controller (PLC or robot controller)
using serial communications. Compared to signal communications using analog signals,
a fieldbus has the following features:
a. Access to signals from multiple devices and multiple data from each device using one
cable.
b. Precise signal transmission since there is no need for A/D conversion and D/A
conversion.
c. Less wiring costs, including signal relay board costs and installation area due to several
dozen (or a hundred) devices connected on one fieldbus.
d. More flexible modification and expansion of a system because multiple devices are
simply added to one fieldbus without additional wiring.
e. Slave devices can transmit self-diagnostics information.
Fieldbus slave function can be added to the RC180 Controller. For each fieldbus on the
controller, there is one board installed. You cannot use more than one fieldbus type on
the same controller.
For master device transmission, up to 256 inputs and 256 outputs are available with
Fieldbus I/O.
Response times for Fieldbus I/O can vary and depend on several factors, including baud
rate, scan rate, number and types of devices, number of SPEL+ tasks, etc.
12.3.2 Response Speed of Fieldbus I/O
Fieldbus I/O communicates the I/O status using serial communication. I/O status
exchange lag occurs according to the serial communication speed. This exchange lag is
also influenced by scan cycle, amount and type of the device, and existence of
communication error.
In the RC180 Controller, status of the Fieldbus I/O is updated approximately every 30 mS.
Although the fieldbus communication speed is fast, response is not available for pulses
less than or equal to 30 mS.
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