12-Channels Pre-programmable Constant Current LED Driver

Version:A.006

Page 11

未經授權而逕予重製、複製、使用或公開本文件，行為人得被追究侵權之相關民刑事責任

Unauthorized reproduction, duplication, use or disclosure of this document will be deemed as infringement.

DM621

Command/Data Switching and Auto-latch Function

Figure 9(a). The Command/Data Method

Figure 9(b). The Auto-latch Method

DM621 combines the signals of DCK and SIN to realize the Command/Data switching

and Auto-latch function. When the area that DCK keeps at high level includes two

positive edges of SIN, DM621 would switch automatically to the command data mode,

illustrated in Figure 9(a). At this time, 8-bits command data could be transmitted to set

the operating condition adequate for different applications. After command data

transmission is accomplished, a latch signal would have to be executed by Auto-latch

function. And this chip would latch command data into internal registers and return to the

grayscale data mode as a latch instruction is executed.

The Auto-latch function is

realized by this method that the area that DCK keeps at high level includes only one

positive edge of SIN, illustrated in Figure 9(b). Note that the latch signal of command

data and grayscale data could be completed according to the same Auto-latch process.

Both Command/Data switching and Auto-latch process would produce signals to control

synchronously every serial DM621s. Therefore, each serial DM621 would enter the

command mode and execute a latch instruction simultaneously.

And DM621 also

supports the internal synchronous clock for grayscale display. These characteristics

would make great grayscale display possible.

In this specific design, the smallest

is 20ns in order to promise the correct command and grayscale data could be received.

Note that command data have to be transmitted to pre-programmed DM621s when the

system is restarted because there are no EEPROM in this chip to save the command data

and the grayscale data.