ST7DALI datasheet(71/141 Pages) STMICROELECTRONICS

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ST7DALI

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DALI COMMUNICATION MODULE (Cont’d)

11.4.3 DALI Standard Protocol

The DALI protocol uses the bi-phase Manchester

asynchronous serial data format. All the bits of the

frame are bi-phase encoded except the two stop

bits.

■ The transmission rate is about 1.2 kHz. The bi-

phase bit period is 833.33 us ±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)

A forward frame consists of 19 bi-phase encoded

bits: 1 start bit (logical ’1’), 1 address byte and 1

data byte. The frame is terminated by 2 stop bits

(idle). The stop bits do not contain any change of

phase.

A backward frame consists of 11 bi-phase encod-

ed bits: 1 start bit (logical ’1’) and 1 data byte. The

frame is terminated by 2 stop bits (idle). The stop

bits do not contain any change of phase.

The transmission rate, expressed as a bandwidth,

is specified at 1.2 kHz for the forward channel and

for the backward channel.

The settling time between two subsequent forward

frames is 9.17 ms (minimum).

The settling time between forward and backward

frames is between 2.92 ms and 9.17 ms. If a back-

ward 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.

After a code violation has occurred, the system is

ready again for data reception.

Figure 42. DALI Standard Frame

stop bits

start bit

address byte

data byte

FORWARD FRAME

start bit

data byte

BACKWARD FRAME

stop bits

BI-PHASE LEVELS

Logical ’1’

Logical ’0’

2T = 833.33 us ±10%

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