Technical data

AS-Interface (AS-i)
1-9
SIMATIC NET AS-Interface – Introduction and Basic Information
C79000-G8976-C089/03
1.3 System Characteristics and Important Data
How the AS-Interface Functions
The AS-Interface/AS-i system operates as outlined below:
S Master-slave access techniques
The AS-i interface is a “single master system”. This means that there is only
one master per AS-i network which controls the data exchange. This polls all
AS-i slaves one after the other and waits for a response.
S Electronic address setting
The address of an AS-i slave is its identifier. This only occurs once within an
AS-Interface system. The setting can either be made using a special
addressing unit or by an AS-i master. The address is always stored
permanently on the AS-i slave. When they are supplied, the AS-i slaves always
have the address “0”.
S Operating reliability and flexibility
The transmission technique used (current modulation) guarantees high
operating reliability. The master monitors the voltage on the cable and the
transferred data. It detects transmission errors and the failure of slaves and
sends a message to the PLC. The user can then react to this message.
Replacing or adding AS-i slaves during normal operation does not affect
communication with other AS-i slaves.
Physical Characteristics
The most important physical characteristics of the AS-Interface and its
components are as follows:
S 2-wire cable for data and power supply
A simple 2-wire cable with a cross section of 2 x 1.5 mm
2
can be used.
Shielding or twisting is not necessary. Both the data and the power are
transferred on this cable. The power available depends on the AS-i power
supply unit used.
For optimum wiring, the mechanically coded AS-i cable is available preventing
the connections being reversed and making simple contact with the AS-i
application modules using the penetration technique.
S Tree structure network with a cable length up to 100 m
The “tree structure” of the AS-Interface allows any point on a cable section to
be used as the start of a new branch. The total length of all subsections can be
up to 100 m.
S Direct integration
Practically all the electronics required for a slave have been integrated on a
special IC. This allows the AS-i connector to be integrated directly in binary
actuators or sensors. All the required components can be installed within a