ST7DALI datasheet(72/141 Pages) STMICROELECTRONICS

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ST7DALI

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DALI COMMUNICATION MODULE (Cont’d)

11.4.4 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 arbi-

tration 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 regis-

ter) in DALI standard format.

The data rate can be changed by writing in the DC-

MCLK 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. Follow-

ing 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 config-

urable. 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.

11.4.5 Functional Description

The user must write to the DCMCLK register to se-

lect the data rate according to the DALI signal fre-

quency.

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 in-

terrupt signal by setting the ITF bit in the DCMCSR

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 ei-

ther 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 Trans-

mit 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.

If the software asks the DCM to receive a "forward

frame", the software must switch the DCM to Re-

ceive state by clearing the RTS bit and setting the

RTA bit in the DCMCR register during the interrupt

routine.

If the ITF interrupt flag is set in the DCMCSR reg-

ister, the software must set the RTA bit in the DC-

MCR register to allow the DCM to perform the next

DALI signal reception or transmission.

The DALIIN signal is always taken into account by

the 4-bit pre-shifter.

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