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AN2708

Basics of DALI

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Basics of DALI

DALI stands for "Digital Addressable Lighting Interface". It is a standard interface for lighting

control solutions, defined by the main lighting manufacturers and standardized as IEC 929.

The DALI protocol is implemented on a master-slave architecture.

It uses the bi-phase Manchester asynchronous serial data format. All the bits of the frame

are bi-phase encoded except the two stop bits. Following are some of the standard features:

●

Transmission rate at 1.2 kHz.

●

Bi-phase bit period is 833.33 µS ±10%.

A forward frame consists of 19 bi-phase encoded bits:

–

1 start bit (0->1: logical '1')

–

1 address byte (8-bit address)

–

1 data byte (8-bit data)

–

2 high level stop bits (no change of phase)

A backward frame consists of 11 bi-phase encoded bits:

–

1 start bit (0->1: logical '1')

–

1 data byte (8-bit data)

–

2 high level stop bits (no change of phase)

Each frame has 2 stop bits which do not contain any change of phase.

The setting time between two subsequent forward frames is 9.17 ms (minimum), while the

delay between forward and backward frame goes from 2.92 ms to 9.17 ms. If a backward

frame has not been started after 9.17 ms, this is interpreted as "no answer".

In the event of code violation, the frame is ignored and the system is ready again for data

reception.

The main advantages of the DALI system can be summarized as follows:

●

Simple wiring: all of the units in the system are interconnected using a simple five-core

cable.

Figure 20.

Cable wiring

AN2708 Datasheet(PDF) 29 Page - STMicroelectronics