Q.Draw the pin diagram of 8051.

The 8051 is a 40-pin DIP whose pins group into four 8-bit ports (P0–P3), power (Vcc, GND), the crystal pins (XTAL1, XTAL2), reset (RST), and the control pins EA, ALE and PSEN.

[!ANSWER]

The 8051 pin diagram is a 40-pin DIP: pins 1–8 = Port 1 (P1.0–P1.7); pin 9 = RST; pins 10–17 = Port 3 (P3.0–P3.7, carrying RXD, TXD, INT0, INT1, T0, T1, WR, RD); pins 18–19 = XTAL2, XTAL1; pin 20 = GND (VSS); pins 21–28 = Port 2 (P2.0–P2.7 = address A8–A15); pin 29 = PSEN; pin 30 = ALE/PROG; pin 31 = EA/VPP; pins 32–39 = Port 0 (P0.7–P0.0 = AD7–AD0); pin 40 = Vcc.

[!TLDR]

The 8051 comes in a 40-pin DIP; its pins carry four 8-bit ports (P0–P3), power (pin 40 Vcc, pin 20 GND), the crystal pins (18, 19), reset (pin 9) and three control pins EA, ALE and PSEN.

The 8051 is packaged in a 40-pin Dual In-line Package (DIP). Pin numbers are written inside the DIP package and the pin names outside. The pins are organised as follows:

Left side (pins 1–20):

• Pins 1–8: Port 1 — P1.0 (bit 0) to P1.7 (bit 7).
• Pin 9: RST — Reset input.
• Pins 10–17: Port 3 — dual-function pins P3.0–P3.7: RXD (receive data), TXD (transmit data), INT0 (interrupt 0), INT1 (interrupt 1), T0 (timer 0 input), T1 (timer 1 input), WR (write strobe), RD (read strobe).
• Pins 18, 19: XTAL2 and XTAL1 — crystal inputs for the oscillator.
• Pin 20: VSS — Ground.

Right side (pins 21–40):

• Pins 21–28: Port 2 — P2.0–P2.7, also carrying the high address lines A8–A15.
• Pin 29: PSEN — Program Store Enable.
• Pin 30: ALE/PROG — Address Latch Enable (also EPROM program pulse).
• Pin 31: EA/VPP — External Enable (also EPROM program voltage).
• Pins 32–39: Port 0 — P0.7–P0.0, also the multiplexed address/data lines AD7–AD0.
• Pin 40: Vcc — power supply (+5 V).

(The signals INT0, INT1, WR, RD, PSEN, PROG and EA are active-low and are shown overbarred in the original.)

[!ANSWER]

The 8051 is a 40-pin DIP: pins 1–8 = Port 1 (P1.0–P1.7); pin 9 = RST; pins 10–17 = Port 3 (P3.0–P3.7 = RXD, TXD, INT0, INT1, T0, T1, WR, RD); pins 18–19 = XTAL2, XTAL1; pin 20 = VSS (GND); pins 21–28 = Port 2 (P2.0–P2.7 = A8–A15); pin 29 = PSEN; pin 30 = ALE/PROG; pin 31 = EA/VPP; pins 32–39 = Port 0 (P0.7–P0.0 = AD7–AD0); pin 40 = Vcc.