UM EN FLX ASI SYS PRO INST - Onlinecomponents.com

UM EN FLX ASI SYS PRO INST
1.4.1 Easy Handling
In the AS-Interface system, the binary I/O device is addressed via the control system (PLC)
in the same way as when using I/O boards and a cable harness. The direct addressing of
devices and the simple electromechanical structure (penetration technique, tree structure)
also simplify retrofitting and the conversion of an AS-i system.
No special knowledge of the system, e.g., for service and maintenance, is required in order
to ensure a smooth transition from the previous star cabling to serial bus technology. The
unerring self-diagnostics of the AS-i system significantly contribute to the reduction of
system downtimes. For example, when replacing a faulty slave device it is not necessary to
assign a new address or modify the PLC program. The AS-Interface system supports the
replacement of a slave through automatic addressing.
1.4.2 Information Content of Data Telegrams
The AS-Interface system is optimized for networking the most basic devices using just a few
items of bit information per device. The data telegrams are therefore very short and have a
very simple structure. This means that the electronics to be integrated in the devices can be
created cost-effectively. The AS-i telegram contains a maximum of four data bits for
information exchange from the control system to the slave (output data) and from the slave
to the control system (input data). Both the input data and the output data are updated in
each cycle.
For more complex devices, e.g., analog devices, larger amounts of data can also be
transmitted. This data must be split and transmitted in several consecutive cycles in
multiplex mode.
1.4.3 Communication Principle
The AS-Interface system is a single master system. A bus access method is used for
communication, which ensures a defined and fast response time. Communication is always
initiated by the master, the slaves only respond to master requests. The master
communicates cyclically with all devices, which are addressed using an address that is
programmed once. A master cycle consists of the requests for all connected devices. This
communication method is known as cyclic polling.
1.4.4 Time Response
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The cycle time of the AS-Interface system is deterministic and proportional to the number of
devices. A time of 150 microseconds is required per device. At full system configuration with
62 devices, the cycle time is 10 milliseconds. At the end of this time, all information that was
transferred from the control system to the Fieldline Extension AS-Interface system (the
master) has arrived at the slaves. Within this time all input data has also been read.
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