LED7708 datasheet(31/53 Pages) STMICROELECTRONICS

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LED7708

Recommended operating conditions

Doc ID 022698 Rev 1

31/53

8.5.4

Brightness data formats

The format for the brightness data is chosen by acting on the BDFS (brightness data format

selector) and the BRLS (brightness register length selector) bits of the DEVCFG1 register.

16x16-bit data format (BDFS=0, BRLS=X)

The brightness registers BRT01:BRT16 are sequentially loaded at the end of 16-bit write

operations. The LE is managed to encode two serial keys: one for the so called “data latch”

operation and another to encode the final “global latch” operation. Therefore, a complete

brightness data transfer to the LED7708 consists of 15 “data latch” operations followed by a

single “global latch” operation.

If the 4096 steps (12-bit) brightness control is used (BRLS low), the four most significant bits

of each brightness register are unused. The brightness registers are written from BRT16 to

BRT01 with auto-decrement after each write operation (the LE signal of the last write

operation to BRT01 must encode a “global latch”).

Figure 9.

16-bit data format, write operation to the brightness register

Table 13.

Brightness data formats

BDFS

BRLS

Brightness data format

16x16, 12-bit

(the 4 most significant bits are not used)

16x16, 16-bit

192x1, 12-bit

256x1, 16-bit

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