89c51 Xtal oscillator

[Sherif Welsen]

Hi every body,

I'm using the 89C51 uc in the circuit that implement digital thermometer.
the circuit uses 12 MHz Xtal oscillator, could any body tell me why the 12MHz specifically? and what happens if we use other oscillator value -if possible- ?

Thanks in advance.

 

[Nigel Goodwin]

Hi every body,

I'm using the 89C51 uc in the circuit that implement digital thermometer.
the circuit uses 12 MHz Xtal oscillator, could any body tell me why the 12MHz specifically? and what happens if we use other oscillator value -if possible- ?

I've never used an 89C51, but generally if you use a different crystal the processor will run at a different speed (fairly obviously). Depending on what the program is doing it 'might' have no effect, but if it uses timings anywhere the timings will obviously be wrong.

If you are writing the program yourself, you write it acording to the clock speed you are using, if you download a program it's likely to have been written using a specific clock frequency.