AS-Interface

The DeltaV system supports the Actuator Sensor-Interface card (AS-Interface) and the Series 2 AS-Interface card in Simplex mode.

The AS-Interface is a digital, serial, bi-directional communications protocol and bus system that interconnects simple binary on/off devices such as actuators, sensors, and discrete devices in the field. The AS-Interface standard is defined by CENELEC standard EN 50295.

The two-conductor AS-Interface cable supplies both power and data for field devices. An AS-Interface network can include branches. The total cable length, (main line and all branches), cannot exceed 100 meters. Refer to the following table for AS-Interface cable distance limits and to the AS-Interface standard (EN 50295) for design and engineering details on AS-Interface cable.

Table: AS-Interface Cable Distance Limits
Item	Specification
Recommended cable	Unshielded AS-Interface yellow cable⁽¹⁾
Distance limits	100 meters total length (main line and branches) without repeater or extender 300 meters total length (main line and branches) with two repeaters⁽²⁾ 300 meters total length (main line and branches) with one extender and one repeater

⁽¹⁾ Any other cable, shielded or unshielded, can be used if the installation meets all the impedance requirements specified in the AS-Interface standard (EN 50295).

⁽²⁾ Repeaters require an additional AS-Interface power supply on the far side of the repeater.

For more information on the AS-Interface and for information on installing AS-Interface devices, refer to the AS-Interface web site at www.as-interface.com.

Installation Notes

The Interface terminal block provides terminations for field wiring for the AS-Interface card and the Series 2 AS-Interface card in Simplex mode.
It is recommended that you do not connect the AS-Interface devices directly to the AS-Interface card terminals. Use one AS-Interface cable to connect the AS-Interface card to the power supply and use another AS-Interface cable to connect the devices to the power supply.
If you are using extenders and repeaters, refer to the device data sheet for additional cabling recommendations.
The AS-Interface bus requires a special AS-Interface power supply (purchased separately) that provides electrical isolation from the data signals. A standard power supply can be used but it must have a conditioning module added to its output. Refer to the AS-Interface standard (EN 50295) for design and engineering details on the AS-Interface power supply.
The "System Power Guidelines" section provides information on extending power to an AS-Interface bus.

Table: AS-Interface Specifications
Item	Specification
Number of ports	Two
Port Type	Actuator Sensor-Interface – 167 kb/second
Isolation	Each port is optically isolated from the system and from each other and factory tested to 1500 VDC.
LocalBus Current	300 mA (max)
24 VDC Field circuit power, per card	None
30 VDC AS-Interface field power per port	70 mA (max)
Mounting	Assigned slot of I/O carrier

Wiring Diagram

Figure: Wiring Diagram for AS-Interface