Friday, July 29, 2011

The AS-Interface Bus for TWIDO PLC

The bus of AS-Interface (Actuator-Sensor-Interface) is a field bus, level 0, and can be applied to connect actuators or sensors. This lets "discrete" or information of analog type to work between the device of sensor/actuator type slave and bus master. AS-Interface is built up of three main essential elements:
• A master of bus,
• A specific contribute providing a 30 VDC voltage,
• One or more devices slave such as sensors, actuators and others.
These components are interrelated by dedicated a two-wire cable to power supply and data transmission.

The Sensors and Actuators major types
Type of sensor describes as following:
1. Sensors and actuators, well-matched with AS-Interface: Thanks to the incorporated feature of AS-Interface, they join directly to the bus of AS-Interface via a connection or T a passive dispatcher.
2. Traditional sensors and actuators, not compatible with AS-Interface: They join to the bus through an interface of AS-Interface (active dispatcher). These interfaces join the traditional actuators and sensors to the bus of AS-Interface and supply them with dialog capacity on the bus.

The AS-Interface V2 Bus Major Specifications
AS-Interface is a system in which switch over management is guaranteed by a single master which, by the bus scanning, calls each sensed slave in succession and awaits a reaction. The master is controlling the parameters, inputs/outputs, and identity each slave codes, as well as their addressing. The frame of serial communications carries for slaves with AS-Interface V2 typical addressing:
• 4 bits data (D0 to D3), which are the inputs or outputs image according to the interface type,
• 4 bits parameter (P0 to P3), which are applied to set the interface operating modes.

The frame of communication series for slaves with extensive addressing settings:
• 4 bits data (D0 to D3), which are the inputs or outputs image according to the interface type,
• 3 bits parameter (P0 to P2), which are applied to set the interface operating modes.

All devices which are used to set the interface of operating modes slave linked to the bus of AS-Interface are recognized by at least one ID code and one I/O Code which completes the slave functional identification. Some slaves have a code of ID1 and ID2, which describe the slave internal functions: on analog slaves, for instance, ID2 demonstrates the slave's analog channel number. The outputs are positioned and input devices of AS-Interface are sent back in the slave's response in the master request of AS-Interface.


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