Only three IO ports are used to drive the eight digit display. MAX7219 supports flicker free displays as well as cascading displays.
MAX7219 is an integrated serial input / output common-cathode display driver, which connects your microprocessor to a 7-segment digital LED display with 8 digits.
This module is compatible with 5V and 3.3V microcontrollers.
VCC and GND should not be connected reversed, so as not to burn the chip
Compatible with Arduino