Continue to Site

Welcome to

Welcome to our site! is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Interfacing 555 and AT89C2051

Not open for further replies.


Advanced Member level 4
Dec 2, 2010
Reaction score
Trophy points
Activity points
I am planning to make a 5 channel chaser circuit. Presently I have a circuit with 555 and 4017 counter, but i think about making one
with AT89C2051 , so that i can do many patterns for the chaser like reverse, forward, 10101,11111,00000 etc...
I can do this with MC but to control and alter the speed i am thinking about feeding the output pulse of 555(speed is controlled by a 100k variable) to input port of MC, is it okay to feed it directly to port (will it damage the port) ,, and also the code??
Presently i have the connection on my bread board the output from pin 3 going to an LED thru a 1k resistor.
Do i need to use an optoisolator?

(I searched thru this forum and i found few questions and one with solution and link to a project of almost the same nature, but the link no longer exists)

You can do everything with the MC, you do not need the 555 and 4017. Everything in SW code

ignore 4017 ok..
As u said i will do it with 89C2051 but how to control the speed , It shouldnt be constant must vary....

each time when it is turned on?????

Give me more detail on your requirements / specifications. You can have a start frequency of 100 Hz and then adjust it up or down with the buttons

Lets not waste much time on this.. Let me get it straight...
My requirement is, i am creating a pulse with 555 timer and giving it to AT89C2051 input port. 5 other ports will be outputs(LEDS).
Based on the 555 pulse the port LED should light accordingly.
Question is how to given the 555 output to MC input.. and process..

Not open for further replies.

Part and Inventory Search

Welcome to