AN1465 Datasheet, PDF (1/14 Pages) Microchip Technology – Digitally Addressable Lighting Interface (DALI) Communication

AN1465
Digitally Addressable Lighting Interface (DALI) Communication
Author: Shaima Husain
Microchip Technology Inc.
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.
FIGURE 1:
DALI FREE-FORM LAYOUT
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.
 2012 Microchip Technology Inc.
DS01465A-page 1