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Problem with high frequency oscillation in AT89C2051 chip

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ITP

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at89c2051 probelm

Hi,

I request your help for this strange problem.

I am using At89C2051 chip for an application. I have connected 10uF across VCC and RESET pin. And 10MHz clock is connected to XTAL1 pin, XTAL2 pin is left open. This 10MHz clock is derived from a 100MHz master clock using CPLD.

My problem is that when I power up the ckt its port(P1) pins shows high frequency oscilations during the reset cycle.This shows some junk characters on the lcd, connected to that port, while on power up.

What could be the problem.

Thanks and regards
Itp
 

at89c2051 problem

use reset signal to control clk input.
 

AT89C2051 Problem

Hi alphi,

Thanks for the response. Can you elaborate your answer. I have connected a cap 10uF at the reset pin of uC. So no reset signal is available outside.

regards
Itp
 

Re: AT89C2051 Problem

Hello,
can it be it due to the pullups lack in P1.0 and P1.1?
Systematically, I always put resistors of about 4k7 (arrays) at inactive level in the pins of the uC.
 

AT89C2051 Problem

Make sure you have also connected a 8.2k resistor between Reset PIN and Ground
 

AT89C2051 Problem

Hi edonor,aamirkhan,

I am not using the P1.0 and P1.1. I have connected 10uF cap between RST pin and VCC, 10k between GND and RST.

I hope, using a seperate 10Hz crystel for the uC may solve the problem, but why this is hapenning is not clear.


Thanks and regards
Itp
 

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