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AT89C51 is a low-voltage, high-performance CMOS 8-bit microcontroller developed by Atmel in the United States. It offers a rich set of internal resources, including 4KB of Flash memory, 128 bytes of RAM, 32 I/O lines, two 16-bit timers/counters, and five interrupt levels. The device also features two full-duplex serial ports, operates within a voltage range of 4.25V to 5.50V, and can run at frequencies from 0 to 24 MHz. One of its key advantages is that it does not require external memory expansion when used.
In this example, we demonstrate how to use Timer 0 (T0) to control LEDs for binary counting using C programming. This project provides a simple yet effective way to understand how the AT89C51 handles timer functions and interacts with output devices like LEDs.
**T0 Control LED for Binary Counting Schematic**
**T0 Control LED for Binary Counting Program Design**
The program works as follows: instead of using key interrupts or external interrupts, we use the counter mode of Timer 0. Each time a button connected to the T0 pin is pressed, the count register is incremented. The current value of the counter is then displayed in binary form using LEDs connected to Port P1.
```c
#include
// Main program
void main() {
TMOD = 0x05; // Timer 0 is configured as a counter, operating in mode 1 (16-bit)
TH0 = 0; // Initialize the high byte of the counter
TL0 = 0; // Initialize the low byte of the counter
TR0 = 1; // Start the timer
while(1) {
P1 = TH0; // Display the high byte of the counter on Port P1
}
}
```
This simple program demonstrates the basic functionality of the AT89C51’s timer in counter mode. By connecting LEDs to Port P1, you can visually observe the binary count as the timer increments. This is a great starting point for learning more advanced timer applications and embedded system programming.
**Recommended Reading: Single-Chip C Language Programming – Timer-Controlled 4 LED Scrolling Flashing**