The MAX7219 is an integrated serial input / output common-cathode display driver, it is connected to a microprocessor with 8-digit 7-segment digital LED display can also be connected to the bar graph display or 64 separate LED. On B BCD encoder including an on-chip, multi-channel scanning loop word drive, but also an 8 x 8 static RAM is used to store each data. Only one external register is used to set the current of each LED segment.