ST7DALIF2 datasheet(92/171 Pages) STMICROELECTRONICS

92 / 171 page

DALI communication module

ST7DALIF2

92/171

16.4

General description

The DCM is able to receive or transmit a serial DALI signal using a 16-bit shift register, an

edge detector, several data/control registers and arbitration logic.

The DCM receives the DALI standard signal from the lighting control network, checks for

errors and loads the address/data bytes of a "forward frame" to the corresponding

DCMFA/DCMFD registers and sends back the data byte of the "backward frame" (written by

software to the DCMBD register) in DALI standard format.

The data rate can be changed by writing in the DCMCLK register (fDATA = 2* fDALI).

fDATA = fCPU/[(N+1)*16]

The DALI standard data rate fDALI is 1.2 kHz. N is the integer value of the DCMCLK register.

Following the above formula, if fCPU is 8 MHz, the integer value of the DCMCLK register is

"207". The bi-phase bit period is 833.33 us ±10%.

The polarity of the bi-phase start bit is not configurable. The start bit is a logical ’1’.

The polarity of the 2 stop bits is not configurable. The 2 stop bits are set to high level.

If an error is detected during reception, the frame will be ignored and the DCM will return to

Receive state.

16.5

Functional description

The user must write to the DCMCLK register to select the data rate according to the DALI

signal frequency.

After Reset, the DCM is in Receive state and waits for the bi-phase start bit (logical ’1’) of

the "forward frame".

The DCM checks the data format of the "forward frame" with the 4-bit pre-shift register. If an

error occurs during reception, the DCM will skip the data and return to the Receive state.

If there is no error in the "forward frame", the data will be shifted Most Significant Bit-first into

the 16-bit shift register. The address byte and the data byte will be loaded to the

corresponding DCMFA and DCMFD registers. The DCM will send an interrupt signal by

setting the ITF bit in the DCMCSR register.

If the software receives an interrupt signal from the DCM, it reads the DCMFA and DCMFD

registers.

Depending on the command, the DCM is able to send back or receive data.

In an interrupt routine, the RTS bit has to be set either before or at the same time as the RTA

bit.

If the software asks the DCM to send back a "backward frame", the software must first write

to the DCMBD register and switch the DCM to Transmit state by setting the RTS and RTA

bits in the DCMCR register during the interrupt routine. The DCMBD register will be shifted

out from the 16-bit shift register in DALI format, the Most Significant Bit-first.

When the "backward frame" has been transmitted, the DCM will send an interrupt signal by

setting the ITF bit in the DCMCSR register.

ST7DALIF2 데이터시트(PDF) 92 Page - STMicroelectronics

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