DALI-2 Fundamentals: Addressing, Groups and Scenes

What is DALI-2?

DALI stands for Digital Addressable Lighting Interface — a two-wire digital bus for lighting control defined by IEC 62386. The bus runs at 16V DC with a maximum current of 250mA per segment. Up to 64 devices (ECGs — Electronic Control Gear, i.e. drivers or ballasts) can share a single bus segment.

Compared to legacy methods: 0-10V control is unidirectional with no feedback from the driver; relay switching is on/off only. DALI-2 provides bidirectional communication — the controller can query every ECG for its actual arc level, fault status, lamp failure, and thermal warnings.

Short address assignment

Each ECG on a DALI bus gets a short address in the range 0–63, assigned during commissioning. The random address algorithm works as follows: the controller broadcasts a "set random address" command; every ECG independently picks a random 24-bit number as its temporary address; the controller then queries addresses sequentially and assigns short addresses one by one.

1. Controller → broadcast: INITIALISE (255)
2. Controller → broadcast: RANDOMISE
   (each ECG picks a 24-bit random address internally)
3. Controller queries: SEARCHADDR H/M/L
   → binary search to isolate each ECG
4. Controller assigns: PROGRAMME SHORT ADDRESS (0..63)
5. Controller → broadcast: TERMINATE

Short address range:  0 – 63  (64 devices max per segment)
Stored in:           ECG non-volatile memory (survives power loss)

Commissioning tools from MDT, Helvar, and Lunatone automate all steps. If an ECG is replaced, it has no short address and must be re-commissioned. The gateway detects the missing short address during its next bus scan.

Groups: 16 per bus

Each ECG can belong to up to 16 groups (group 0–15), and can be a member of multiple groups simultaneously. Groups are the primary tool for zone control: a single "Group 1 recall scene 3" command causes every ECG in group 1 to fade to its stored scene 3 value — with no further traffic on the bus after the command.

Scenes: 16 per ECG

Each ECG stores 16 scene values (scene 0–15). A scene value is an arc level in the range 0–254 (where 254 = 100% output; 255 = MASK — do not change). For DALI-2 DT8 colour devices, each scene additionally stores colour temperature (Tc) and/or XY colour coordinates.

Fade time is also stored per scene in ECG memory (configurable from 0.7 seconds to 90 minutes). Scene values are programmed during commissioning and survive power cycles — the ECG holds them in non-volatile flash.

DALI-2 vs DALI (original)

KNX–DALI integration

The DALI-2 bus is controlled by a DALI-2 gateway that is itself a KNX bus device. The gateway translates KNX group address telegrams into DALI-2 bus commands — and in the reverse direction, reports ECG status back to KNX. Typical KNX datapoint mappings:

KNX DPT 1.001  (1-bit on/off)   → DALI group ON / OFF (arc 254 / 0)
KNX DPT 3.007  (4-bit dim)      → DALI relative dim up/down
KNX DPT 5.001  (8-bit 0–100%)  → DALI absolute arc level (direct)
KNX DPT 18.001 (8-bit scene)   → DALI group scene recall

Example: GA 3/1/0 (DPT 1.001) → DALI Group 1 ON/OFF
         GA 3/1/1 (DPT 5.001) → DALI Group 1 arc level 0–100%
         GA 3/1/5 (DPT 18.001)→ DALI Group 1 scene 0–15 recall