AS-Interface basics

What opportunities does AS-Interface offer?

Companies worldwide are relying on simple wiring and automation technologies to improve their overall plant efficiency and availability. Always present: AS-Interface. The sophisticated AS-Interface technology offers high reliability, noise immunity and diverse diagnostic capabilities.

The simple, very stable and proven technology enables sensors to simultaneously transmit diagnostic information to the PLC and to higher-level IT infrastructures. Its modular structure and flexible connection technology ensure easy integration into the system.

A two-wire flat cable transmits data and energy, eliminating complex parallel wiring.

Below we have summarised the most important facts and benefits of AS-Interface for you.

AS-i key data:

Topology	flexible structure
Medium	unshielded two-wire line for data and energy
Cable length	100 m, expandable to up to 1,000 m, up to 3,000 m possible through fibre optics
Number of I/Os	496 inputs + 496 outputs for digital, analogue and safe data
Cycle time	5 - 10 ms

What components make up the AS-i System?

Components	Description
Required:
AS-i master	The AS-i master controls traffic over the AS-i network.
AS-i power supply	The AS-i power supply is a specialty power supply that generates a regulated DC output voltage between 29.5 V and 31.6 V according to the AS-i specification.
Network flat cable	Yellow flat cable carries communication and input power to AS-i modules.
AS-i I/O modules	Used to connect binary sensors and output devices to the network.
Optional: (Necessary if auxiliary power is required for output devices)
24 VDC power supply	A standard 24 VDC power supply is used to supply power to output devices via the black flat cable.
Auxiliary power flat cable	Black flat cable carries 24 VDC output power to the AS-i modules.

AS-i topologies could not be more flexible

Below are examples of different AS-i cable topologies that are used for wiring systems and applications. These different topologies can be used in combination with eachother.

Line	Tree
Star	Ring

Maximum cable length of an AS-i segment is 100 m

The standard maximum cable length of an AS-i segment, without accessories, is 100 m. Every meter of AS-i cable length counts towards the 100 m.

What happens if the AS-i cable length exceeds 100 m?

Communication problems can occur due to unwanted signal reflections on the cable.
- Solution: AS-i bus termination accessory, AC1147
Excess voltage drop causing the AS-i slaves at the end of the cable to receive an insufficient amount of power (Ohm's law)
- Solution: AS-i repeater, AC3226

AS-i bus termination or terminating resistor, AC1147	Improves AS-i signal quality Used to extend AS-i installations up to a maximum of 200 m Can only be used for cable lengths exceeding 100 m only one AS-i bus termination per 200 m AS-i segment Must install as far away as possible from the AS-i power supply Does not require an AS-i address LEDs indicate monitoring of the supply voltage Yellow: AS-i voltage > 18.5 V Green: AS-i voltage > 26 V
AS-i repeater, AC3226	Extends the AS-i network by another AS-i segment Requires an additional AS-i power supply to supply the subsequent AS-i segment Does not require an AS-i address Allows AS-i slaves before and after the repeater A maximum of three AS-i segments can be connected in series using no more than two repeaters
Fiber optic repeater, AC3227	Used to bridge long distances of up to 3,000 m Can be used with other accessories to increase the AS-i cable length Very low EMC susceptibility Allows galvanic decoupling of AS-i segments. (ex.- separation of outdoor and indoor installations) Always used in pairs bus termination that can be optionally enabled. It is not possible to install AS-i slaves within the fiber optic segment. Fiber optic cable 50/125 µm with ST connector (recommended up to 500 m) Fiber optic cable 62.5/125 µm with ST connector (do not use for distances less than 200 m)

AS-i ClassicLine modules

An animation shows the toolless quick mounting technology.

The user can insert the flat cable into the module lower part in three different directions. A slide locks the upper part and lower part.