Regardiing 8051 reset circuit

[tarun embedded lover]

If I connect 22uf capacitor and 10k resistance in place of 10uf and 8.2k resistance it works fine can any body explain.

 

[FvM]

Counterquestion, which exact 8051 type?

 

[barry]

What is your question? Why does the reset circuit work with short or long time constants?

 

[andre_luis]

Reset
A reset is accomplished by holding the RST pin high for at least two machine cycles (24 oscillator periods), while the oscillator is running. To insure a good power-up reset, the RST pin must be high long enough to allow the oscillator time to start up (normally a few milliseconds) plus two machine cycles.

Both R-C options yield very close result at the same magnitude order, and complies to timing requirement stated for RST pin at most 51 cores ( e.g. ) .


+++

 

[tarun embedded lover]

AT89C51 or AT89S52

 

[FvM]

AT89C51 or AT89S52

You'll find in the datasheet that CMOS 8051 (all recent types) can work without a pulldown resistor and only 1 µF capacitor. In other words, any RC combination that achieves a reasonable delay will be fine.