6 Unisolated ASI-interface bus application diagram

PCLT-2A

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6

Unisolated ASI-interface bus application diagram

6.1

AS-Interface Bus application overview

The AS-Interface bus is a low-end field bus for actuators and sensors in manufacturing &

industrial automation. Its electrical architecture uses an unshielded 2-wire yellow cable that

transports both the 24 V power supply of the field nodes and the serial bi-directional data

communication.

Figure 13. Simplified architecture of AS-Interface bus.

The data communication is achieved with a current carrier modulation superimposed over the

power wires. Therefore, the power bus terminals are filtered in order to maintain identical and

calibrated differential and common mode impedances measured by both master and slave

units.

6.2

Isolation of the sensor section and the supply from data/supply

bus

The PCLT can be designed as an interface between a proximity sensor and its associated slave

controller unit.

The sensor power supply is generated from the bus power supply with a filter and a regulator

that are inserted in the slave unit. In the same manner, the sensor logic signal is isolated from

the AS- Interface power supply bus to avoid any degradation of the data transmission.

A conventional way to achieve the interface with the PCLT and the AS- Interface controller is to

insert an opto-coupler between the AS-Interface controller and the PCLT that runs in opto-

coupler mode as shown on figure 1 (MOD=0).

I/O SLAVE

AS-i SLAVES

AS-i MASTER

I/O SLAVE

I/O SLAVE

I/O SLAVE

AS-i SLAVES

AS-i MASTER

I/O SLAVE

I/O SLAVE