The MAX7219 is an integrated serial input / output common-cathode display driver that connects the microprocessor to an 8-digit 7-segment digital LED display, and can be connected to a bargraph display or 64 individual LEDs.
On a board include B-type BCD encoder, multi-scan loop, paragraph word drive, but also an 8 * 8 static RA is used to store each data. Only one external register is used to set the segment current for each LED.
A convenient four-wire serial interface can be connected to all common microprocessors. Each data can be addressed, the update does not need to rewrite all the display, MAX7219 also allows the user to select for each data encoding or not encoded.
The entire device includes a 150μA low power shutdown mode, analog and digital brightness control, a scan limit register allows the user to display 1-8 bits of data, there is a let LED light detection mode. Only need 3 IO mouth can drive a lattice! Dot matrix display without flicker! Support cascade!
Operating Voltage: 5V
A single module can drive a 8x8 dot matrix common cathode
Module with input and output interfaces, support for cascading multiple modules

The left side of the module to the input port, the right to an output port
When the control of a single module, simply input port connected to CPU
When a plurality of cascaded modules, input and output termination CPU, an input terminal of the second output end of the first module a module, the first two modules of the input terminal of the three termination modules, and so on...
For example:51 microcontrollers,
VCC → 5V.
GND → GND.
DIN → P2.2.
CS → P2.1.
CLK → P2.0.

Package Included:
1x MAX7219 Dot Matrix Module 4-in-1
1x 20cm DuPont line 5pin