This is an experimental board for ATTiny2313 microcontroller that provides a 10-pin connector for in-circuit serial programming, and other header pins to access I/O pins. The AT2313 microcontroller runs on an external 10Mhz crystal. The board has a push button reset switch for resetting the microcontroller.
The onboard regulator provides a +5V DC to the microcontroller. The board is also featured with a DB9 connector to communicate with a PC through RS232 port. The TTL to RS232 level translation is achieved through a MAX232 chip. The circuit for this board is very simple to build, and the PCB layout is also available. This is a good board for learning AVR microcontroller.
For more detail: Experimental board using ATTiny2313 microcontroller