Onboard 4M crystal oscillator, the socket crystal frequency can be replaced at any time. ^^ The 4-bit independent keyboard is connected to RB0 RB1 RB2 RB3. External 5V DC power interface (send USB power cable without additional purchase). ^^ 8 LEDs are connected to the RD port. When the J3 is plugged in, the LED is enabled. J3 is unplugged and the RD port is completely released. ^^ Standard RS232 communication interface, microcontroller board and computer communication interface. ICSP programming simulation interface (can be connected to K150 ICD2 and other tools).
^^ VCC GND pin header power extension interface for access or -out of 5 volt power supplies. All IO ports of the MCU are easily extended by using pin headers. ^^ ^^ ^^ ^^ ^^