MAX7219 is an integrated serial input / output common-cathode display driver, it connects the microprocessor with 8 digits 7-segment digital LED display, you can also connect a bar graph display or 64 independent LEDs. This item not only includes a B-type BCD encoder chip, multi-channel scanning loop, segment and word driver, but also a 8 * 8 static RAM for storing each data. Only one external register that used to set the segment current of each LED. A convenient four-wire serial interface that can be connected to all general-purpose microprocessor. Each data can be addressed in the update without rewriting all of the display. MAX7219 also allows each user to select a data coding or non-coding. The entire device contains a 150μA low-power shutdown mode, analog and digital brightness control, a scan-limit register that allows the user to display 1-8 bits data, and one mode for all LED luminescence detection. It requires only three IO ports to drive a dot matrix! No flicker when the dot matrix display! Support cascading!