Introduction to the pins and functions of 80C51 microcontroller

First, let’s connect the pin diagram of the microcontroller. If so, the specific functions are introduced below.

The 40 pins of the microcontroller can be roughly divided into 4 categories: power, clock, control and I/O pins.

⒈ Power supply: ⑴ VCC - chip power supply, connected to +5V;

⑵ VSS - ground terminal;

⒉ Clock: XTAL1, XTAL2 - the inverting input and output terminals of the crystal oscillator circuit.

⒊ Control lines: There are 4 control lines in total.

⑴ ALE/PROG: Address latch enable/on-chip EPROM programming pulse

① ALE function: used to latch the lower 8-bit address sent from port P0

② PROG function: For chips with EPROM inside the chip, during EPROM programming, this pin inputs programming pulses.

⑵ PSEN: External ROM read strobe signal.

⑶ RST/VPD: reset/standby power supply.

① RST (Reset) function: reset signal input terminal.

② VPD function: connect to backup power supply when Vcc loses power.

⑷ EA/Vpp: Internal and external ROM selection/on-chip EPROM programming power supply.

① EA function: internal and external ROM selection terminal.

② Vpp function: For chips with EPROM inside the chip, during EPROM programming, the programming power Vpp is applied.

⒋ I/O line

80C51 has a total of four 8-bit parallel I/O ports: P0, P1, P2, and P3 ports, with a total of 32 pins. Port P3 also has a second function, used for special signal input and output and control signals (belonging to the control bus).

〈51 microcontroller pin diagram and pin functions〉