8051 Ports
8051 has 32-gpio's grouped into 4-Ports namely P0-P3 as shown in the below table.
| PORT | Number of Pins | Alternative Function |
| P0 | 8 (P0.0-P0.7) | AD0-AD7 (Address and Data bus) |
| P1 | 8 (P1.0-P1.7) | None |
| P2 | 8 (P2.0-P2.7) | A8-A15 (Higher Address Bus) |
| P3 | 8 (P3.0-P3.7) | UART, Interrupts, (T0/T1)Counters |
Hardware Connections
Program:
| //Program by UdayaPrakashJayaraman
|
| #include <reg51.h>
|
| void delay(unsigned int Count) |
| { |
| unsigned int i,j; |
| for(i=0;i<Count;i++) |
| { |
| for(j=0;j<100;j++); |
| } |
| } |
| int main() |
| {
P2=0xff; //Default HIGH to configure pins in Negative switching |
| while(1) |
| { |
| P2 = 0x00; /* Turn ON all the leds connected to P2 */ |
| delay(500); |
| |
| P2 = 0x11; /* Turn OFF all the leds connected to P2 */ |
| delay(500); |
| } |
| return (0); |
| } |
Example 2
In this example, we will see how to access a single port pin to blink the LED.
| //Program by UdayaPrakashJayaraman |
| #include <reg51.h>
|
| sbit LED = P2^0; // Bling the single LED connected to P2.0 |
| |
| void delay(unsigned int Count) |
| { |
| unsigned int i,j; |
| for(i=0;i<Count;i++) |
| { |
| for(j=0;j<100;j++); |
| } |
| } |
| |
| int main() |
| { |
| while(1) |
| { |
| LED = 1; /* Turn ON the LED connected to P2.0 */ |
| delay(500); |
| |
| LED = 0; /* Turn OFF the LED connected to P2.0 */ |
| delay(500); |
| } |
| return (0); |
| } |
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