This is a pretty old circuit, but I found it interesting to describe here.
24×24 LED display is formed by using nine 8×8 Dot LED matrix displays, that are connected to AT90S2313 MCU. MCU scans an indicator line in series. Special PC program is written which allows drawing images on screen and transfer them via a COM port to the device. You can send pictures in series what gives an animation effect.
The circuit is built using obsolete AT90S2313 MCU which can be replaced by Attiny2313 MCU with minor modifications of firmware.
To make program work you event don’t need to connect the device to the computer COM port. You can store images in other master MCU EEPROM memory Each received byte from UART is immediately sent to 8 LEDs, the second byte to next 8 LEDs and so on. Bytes has to be addressed one by one without delay. USART is working at 115200 baud, 8bits, no parity.
Demo movie (137kB);
Originals source svv.on.ufanet.ru