hi;
I want to make a circuit based on 8051 and ne555 (as external oscillator).That can controlled the blinking rate (gape between off time and on time of led).The 100k variable preset controller is add with 555. That can control the blinking speed of this circuit.

we know that changing value of crystal oscillator can change the blinking rate/speed.But in that circuit we use 12Mhz crystal and it is fixed.So we add that external 555 as oscillator to add extra clock pulse in at 89s52.It definitely change the blinking rate/speed.
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Is it possible to make my idea.If yes can anyone help me to build it. How can i get progress and ideas.what is the exact logic?I need assembly code to attached ne555 as oscillator.Or any sample code for similar project.Or specific code for this circuit in assembly language.

 

You can connect a 555 timer to pretty much any microcontroller to act as the frequency source if the chip has a CLKIN pin (which the 8051 does have AFAIK.) I would recommend a CMOS timer such as a TLC555, they are capable of operating up to 2.1 MHz with appropriate components, and the output goes to both rails, which is important for an external clock source.

 

Why not program the 8051 to do all the timing. You can make it do almost anything. Flash at different rates and sequences. You could even use multiple LEDs and do some really fancy stuff.

 

Have you read this?

LEDs, 555s, Flashers, and Light Chasers