 2012 Microchip Technology Inc.

DS01465A-page 1

AN1465

The Digitally Addressable Lighting Interface (DALI) has

emerged as a standard in Europe to address growing

power issues, mostly for commercial and industrial

purposes. DALI is part of the IEC 60929 specification,

and relates specifically to digitally controlled dimmable

fluorescent ballasts. DALI type ballasts can run at lower

power levels than standard magnetic ballasts.

Commercial development of DALI started around 1998.

DALI consists of a two-wire serial bus and requires a

special DALI power supply. The Master sends 16-bit

Manchester encoded data packets, and the ballasts

can respond with an 8-bit Manchester encoded data

packet. Multi-Masters are allowed, and two Masters

can share the same ballast. There are 64 channels, or

individual addresses, available for the ballasts to be

connected to one interface line. Each DALI bus can

have 16 groups at the maximum, and there are 16

scenes available. There is no error checking in the

DALI protocol. This application note describes the

basic communication between the control device and

the control gear, which includes explanation of

electrical specifications, timing, packet formats and

Manchester encoding/decoding.

TERMINOLOGY

• Control Gear: Ballast or Sensor/Receiver

• Control Device: Controller/Transmitter

• Forward Frame: Packet sent from the control

device to the control gear

• Backward Frame: Response packet sent from

the control gear to the control device

• Short Address: Address of an individual control

gear in the system

• Group Address: Address to a group of control

gear

• Broadcast: Address used to address all the

control gears at once

• Direct Arc Power: Power level sent to an individ-

ual ballast or sent as a broadcast to all control

gear, to immediately set the lamps to that power

level

PHYSICAL LAYER

Topology

Unlike analog systems, DALI does not require any hard-

wired power circuit control groups. The combination of

individual ballast addressing with digital switching

eliminates vertical switch wiring. DALI has a free-form

layout (Figure 1). Daisy chain, star topology and multi-

drop are all allowed. A combination of two or more

topologies is also allowed.

FIGURE 1:

DALI FREE-FORM LAYOUT

Author:

Shaima Husain

Microchip Technology Inc.

Digitally Addressable Lighting Interface (DALI) Communication