Instruction manual for devices of the MASI20 series
6
V 1.0
2 System description
2.1 AS-i system
The AS-Interface is a simple and cost-saving wiring system based on a 2-wire cable for data and power
transmission to sensors over a distance of up to 100 m. System expansion > 100 m is possible with the
use of repeaters.
The application area concentrates mainly on lower level industrial automation for networking simple and
mostly binary sensors and actuators.
The AS-Interface is a substitute for traditional wiring between sensors, actuators and the PLC. System-
based mechanisms effectively support setup, operation and maintenance.
Every AS-Interface system requires a control unit, the master. This is available as a PLC specific module,
a PC card or a gateway. The application program on the control system or PC controls the decentralized
I/O groups (slaves) via the master. The master performs cyclical information exchange between the
master and the slaves independently. According to standard specifications, an AS-Interface network
supports the operation of maximum 31 slaves. According to extended specifications, it supports the
operation of maximum 62 modules.
There are two types of slaves : active and passive modules.
Active modules are slaves with interfaces linking to common binary sensors and actuators. Each data
transmission cycle between the master and the slave is limited to 4 input data bits and 4 output data bits.
This kind of structure and the length of the data messages support the operation of up to 124 inputs and
124 outputs (standard specifications).
The extended specification supports the operation of 248 inputs and 186 outputs.
Passive modules are typically fitted with a standard electromechanical interface (for ex. round plug
connector M12) for a direct connection of sensors and actuators to the AS-Interface integrated into the
field bus cable.
In order to ensure an accurate data transmission between the master and the slaves, each slave - A or B
- must be assigned to a specific address configurable from 1 to 31.
Addressing can either be performed by a manual addressing device or by the master itself.
AS-Interface products are generally marked by specific logos. Such identifications allow to distinguish
between certified products and such products that are AS-Interface certified by the manufacturer.
Fig. 2-1 : AS-Interface
Fig. 2-2 : Certification
